docs: Fix Sphinx 3.x warnings, and enable warnings-as-errors on build.

This enables warnings as errors and fixes all current errors, namely:

- reference to terms in the glossary must now be explicit (:term:)
- method overloads must not be declared as a separate method or must
  use :noindex:
- 2 cases where `` should have been used instead of `

docs/library/esp32.rst

@@ -84,9 +84,9 @@ methods to enable over-the-air (OTA) updates.
     Returns a 6-tuple ``(type, subtype, addr, size, label, encrypted)``.
 
 .. method:: Partition.readblocks(block_num, buf)
-.. method:: Partition.readblocks(block_num, buf, offset)
+            Partition.readblocks(block_num, buf, offset)
 .. method:: Partition.writeblocks(block_num, buf)
-.. method:: Partition.writeblocks(block_num, buf, offset)
+            Partition.writeblocks(block_num, buf, offset)
 .. method:: Partition.ioctl(cmd, arg)
 
     These methods implement the simple and :ref:`extended

docs/library/index.rst

@@ -23,7 +23,7 @@ into MicroPython. There are a few categories of such modules:
 * Modules which implement a subset of Python functionality, with a provision
   for extension by the user (via Python code).
 * Modules which implement MicroPython extensions to the Python standard libraries.
-* Modules specific to a particular `MicroPython port` and thus not portable.
+* Modules specific to a particular :term:`MicroPython port` and thus not portable.
 
 Note about the availability of the modules and their contents: This documentation
 in general aspires to describe all modules and functions/classes which are
@@ -38,7 +38,7 @@ in a module (or even the entire module) described in this documentation **may be
 unavailable** in a particular build of MicroPython on a particular system. The
 best place to find general information of the availability/non-availability
 of a particular feature is the "General Information" section which contains
-information pertaining to a specific `MicroPython port`.
+information pertaining to a specific :term:`MicroPython port`.
 
 On some ports you are able to discover the available, built-in libraries that
 can be imported by entering the following at the REPL::

docs/library/micropython.rst

@@ -100,7 +100,7 @@ Functions
    unlocked.
 
    Note: `heap_locked()` is not enabled on most ports by default,
-   requires `MICROPY_PY_MICROPYTHON_HEAP_LOCKED`.
+   requires ``MICROPY_PY_MICROPYTHON_HEAP_LOCKED``.
 
 .. function:: kbd_intr(chr)
 

docs/library/network.WLAN.rst

@@ -101,7 +101,7 @@ Methods
     nic.ifconfig(('192.168.0.4', '255.255.255.0', '192.168.0.1', '8.8.8.8'))
 
 .. method:: WLAN.config('param')
-.. method:: WLAN.config(param=value, ...)
+            WLAN.config(param=value, ...)
 
    Get or set general network interface parameters. These methods allow to work
    with additional parameters beyond standard IP configuration (as dealt with by
@@ -117,7 +117,7 @@ Methods
     print(ap.config('channel'))
 
    Following are commonly supported parameters (availability of a specific parameter
-   depends on network technology type, driver, and `MicroPython port`).
+   depends on network technology type, driver, and :term:`MicroPython port`).
 
    =============  ===========
    Parameter      Description

docs/library/network.rst

@@ -39,7 +39,7 @@ Common network adapter interface
 ================================
 
 This section describes an (implied) abstract base class for all network
-interface classes implemented by `MicroPython ports <MicroPython port>`
+interface classes implemented by :term:`MicroPython ports <MicroPython port>`
 for different hardware. This means that MicroPython does not actually
 provide ``AbstractNIC`` class, but any actual NIC class, as described
 in the following sections, implements methods as described here.

docs/library/pyb.Flash.rst

@@ -26,6 +26,7 @@ Constructors
    This constructor is deprecated and will be removed in a future version of MicroPython.
 
 .. class:: pyb.Flash(\*, start=-1, len=-1)
+   :noindex:
 
    Create and return a block device that accesses the flash at the specified offset. The length defaults to the remaining size of the device.
 
@@ -35,9 +36,9 @@ Methods
 -------
 
 .. method:: Flash.readblocks(block_num, buf)
-.. method:: Flash.readblocks(block_num, buf, offset)
+            Flash.readblocks(block_num, buf, offset)
 .. method:: Flash.writeblocks(block_num, buf)
-.. method:: Flash.writeblocks(block_num, buf, offset)
+            Flash.writeblocks(block_num, buf, offset)
 .. method:: Flash.ioctl(cmd, arg)
 
     These methods implement the simple and :ref:`extended

docs/library/uerrno.rst

@@ -7,7 +7,7 @@
 |see_cpython_module| :mod:`python:errno`.
 
 This module provides access to symbolic error codes for `OSError` exception.
-A particular inventory of codes depends on `MicroPython port`.
+A particular inventory of codes depends on :term:`MicroPython port`.
 
 Constants
 ---------
@@ -16,7 +16,7 @@ Constants
 
     Error codes, based on ANSI C/POSIX standard. All error codes start with
     "E". As mentioned above, inventory of the codes depends on
-    `MicroPython port`. Errors are usually accessible as ``exc.args[0]``
+    :term:`MicroPython port`. Errors are usually accessible as ``exc.args[0]``
     where ``exc`` is an instance of `OSError`. Usage example::
 
         try:

docs/library/uio.rst

@@ -114,7 +114,9 @@ Classes
         Get the current contents of the underlying buffer which holds data.
 
 .. class:: StringIO(alloc_size)
+    :noindex:
 .. class:: BytesIO(alloc_size)
+    :noindex:
 
     Create an empty `StringIO`/`BytesIO` object, preallocated to hold up
     to *alloc_size* number of bytes. That means that writing that amount

docs/library/uos.rst

@@ -252,7 +252,7 @@ that the block device supports the extended interface.
     dependent on the specific block device.
 
     .. method:: readblocks(block_num, buf)
-    .. method:: readblocks(block_num, buf, offset)
+                readblocks(block_num, buf, offset)
 
         The first form reads aligned, multiples of blocks.
         Starting at the block given by the index *block_num*, read blocks from
@@ -267,7 +267,7 @@ that the block device supports the extended interface.
         The number of bytes to read is given by the length of *buf*.
 
     .. method:: writeblocks(block_num, buf)
-    .. method:: writeblocks(block_num, buf, offset)
+                writeblocks(block_num, buf, offset)
 
         The first form writes aligned, multiples of blocks, and requires that the
         blocks that are written to be first erased (if necessary) by this method.

docs/library/ure.rst

@@ -138,12 +138,12 @@ Functions
    If *count* is specified and non-zero then substitution will stop after
    this many substitutions are made.  The *flags* argument is ignored.
 
-   Note: availability of this function depends on `MicroPython port`.
+   Note: availability of this function depends on :term:`MicroPython port`.
 
 .. data:: DEBUG
 
    Flag value, display debug information about compiled expression.
-   (Availability depends on `MicroPython port`.)
+   (Availability depends on :term:`MicroPython port`.)
 
 
 .. _regex:
@@ -184,7 +184,7 @@ to the replacement function in `sub()`.
 
    Return a tuple containing all the substrings of the groups of the match.
 
-   Note: availability of this method depends on `MicroPython port`.
+   Note: availability of this method depends on :term:`MicroPython port`.
 
 .. method:: match.start([index])
             match.end([index])
@@ -193,10 +193,10 @@ to the replacement function in `sub()`.
    substring group that was matched.  *index* defaults to the entire
    group, otherwise it will select a group.
 
-   Note: availability of these methods depends on `MicroPython port`.
+   Note: availability of these methods depends on :term:`MicroPython port`.
 
 .. method:: match.span([index])
 
    Returns the 2-tuple ``(match.start(index), match.end(index))``.
 
-   Note: availability of this method depends on `MicroPython port`.
+   Note: availability of this method depends on :term:`MicroPython port`.

docs/library/usocket.rst

@@ -37,8 +37,8 @@ power) and portable way to work with addresses.
 However, ``socket`` module (note the difference with native MicroPython
 ``usocket`` module described here) provides CPython-compatible way to specify
 addresses using tuples, as described below. Note that depending on a
-`MicroPython port`, ``socket`` module can be builtin or need to be
-installed from `micropython-lib` (as in the case of `MicroPython Unix port`),
+:term:`MicroPython port`, ``socket`` module can be builtin or need to be
+installed from `micropython-lib` (as in the case of :term:`MicroPython Unix port`),
 and some ports still accept only numeric addresses in the tuple format,
 and require to use `getaddrinfo` function to resolve domain names.
 
@@ -61,7 +61,7 @@ Tuple address format for ``socket`` module:
   must be 0. *scopeid* is the interface scope identifier for link-local
   addresses. Note the domain names are not accepted as *ipv6_address*,
   they should be resolved first using `usocket.getaddrinfo()`. Availability
-  of IPv6 support depends on a `MicroPython port`.
+  of IPv6 support depends on a :term:`MicroPython port`.
 
 Functions
 ---------
@@ -81,7 +81,7 @@ Functions
 
 .. function:: getaddrinfo(host, port, af=0, type=0, proto=0, flags=0, /)
 
-   Translate the host/port argument into a sequence of 5-tuples that contain all the 
+   Translate the host/port argument into a sequence of 5-tuples that contain all the
    necessary arguments for creating a socket connected to that service. Arguments
    *af*, *type*, and *proto* (which have the same meaning as for the `socket()` function)
    can be used to filter which kind of addresses are returned. If a parameter is not
@@ -141,7 +141,7 @@ Constants
 .. data:: AF_INET
           AF_INET6
 
-   Address family types. Availability depends on a particular `MicroPython port`.
+   Address family types. Availability depends on a particular :term:`MicroPython port`.
 
 .. data:: SOCK_STREAM
           SOCK_DGRAM
@@ -151,7 +151,7 @@ Constants
 .. data:: IPPROTO_UDP
           IPPROTO_TCP
 
-   IP protocol numbers. Availability depends on a particular `MicroPython port`.
+   IP protocol numbers. Availability depends on a particular :term:`MicroPython port`.
    Note that you don't need to specify these in a call to `usocket.socket()`,
    because `SOCK_STREAM` socket type automatically selects `IPPROTO_TCP`, and
    `SOCK_DGRAM` - `IPPROTO_UDP`. Thus, the only real use of these constants
@@ -160,12 +160,12 @@ Constants
 .. data:: usocket.SOL_*
 
    Socket option levels (an argument to `setsockopt()`). The exact
-   inventory depends on a `MicroPython port`.
+   inventory depends on a :term:`MicroPython port`.
 
 .. data:: usocket.SO_*
 
    Socket options (an argument to `setsockopt()`). The exact
-   inventory depends on a `MicroPython port`.
+   inventory depends on a :term:`MicroPython port`.
 
 Constants specific to WiPy:
 
@@ -185,7 +185,7 @@ Methods
    on the socket object will fail. The remote end will receive EOF indication if
    supported by protocol.
 
-   Sockets are automatically closed when they are garbage-collected, but it is recommended 
+   Sockets are automatically closed when they are garbage-collected, but it is recommended
    to `close()` them explicitly as soon you finished working with them.
 
 .. method:: socket.bind(address)
@@ -259,7 +259,7 @@ Methods
    completed. If zero is given, the socket is put in non-blocking mode. If None is given, the socket
    is put in blocking mode.
 
-   Not every `MicroPython port` supports this method. A more portable and
+   Not every :term:`MicroPython port` supports this method. A more portable and
    generic solution is to use `uselect.poll` object. This allows to wait on
    multiple objects at the same time (and not just on sockets, but on generic
    `stream` objects which support polling). Example::

docs/library/ussl.rst

@@ -24,7 +24,7 @@ Functions
    :meth:`~usocket.socket.accept()` on a non-SSL listening server socket.
 
    Depending on the underlying module implementation in a particular
-   `MicroPython port`, some or all keyword arguments above may be not supported.
+   :term:`MicroPython port`, some or all keyword arguments above may be not supported.
 
 .. warning::