zephyr: Add support for GC split-heap.

Adds the ability to use PSRAM and non-contiguous memory.

Example usage, add this to dts overlay:

    / {
            heap_psram {
                    compatible = "micropython,heap";
                    size = <DT_SIZE_M(4)>;
                    memory-region = <&psram>;
            };

            heap_sram1 {
                    compatible = "micropython,heap";
                    size = <DT_SIZE_K(140)>;
                    memory-region = <&sram1>;
            };
    };

Signed-off-by: Vdragon <mail@massdriver.space>

ports/zephyr/dts/bindings/micropython/micropython,heap.yaml

@@ -0,0 +1,23 @@
+# Copyright (c) 2025 MASSDRIVER EI (massdriver.space)
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+    MicroPython Heap
+    Used to define micropython heap areas.
+
+compatible: "micropython,heap"
+
+include: [base.yaml]
+
+properties:
+  size:
+    type: int
+    required: true
+    description: |
+      Size of the heap
+
+  memory-region:
+    type: phandle
+    required: true
+    description: |
+      Memory region to place the heap in

ports/zephyr/main.c

@@ -58,6 +58,28 @@
 #include "extmod/vfs.h"
 #endif
 
+#if MICROPY_ENABLE_GC
+#if MICROPY_GC_SPLIT_HEAP && DT_HAS_COMPAT_STATUS_OKAY(micropython_heap)
+
+#include <zephyr/linker/devicetree_regions.h>
+
+#define MICROPY_HEAP_NAME(node) CONCAT(DT_NODE_FULL_NAME_TOKEN(node), _heap)
+
+#define MICROPY_HEAP_DEFINE(node) \
+    static char MICROPY_HEAP_NAME(node)[DT_PROP(node, size)] \
+    Z_GENERIC_SECTION(LINKER_DT_NODE_REGION_NAME(DT_PROP(node, memory_region)));
+
+DT_FOREACH_STATUS_OKAY(micropython_heap, MICROPY_HEAP_DEFINE)
+
+#define MICROPY_HEAP_ADD(node) \
+    gc_add((void *)&MICROPY_HEAP_NAME(node), \
+    (void *)&(MICROPY_HEAP_NAME(node)[DT_PROP(node, size) - 1]));
+
+#elif DT_HAS_COMPAT_STATUS_OKAY(micropython_heap)
+#error Has additional Heap but split heap is not enabled
+#endif
+#endif
+
 #include "modmachine.h"
 #include "modzephyr.h"
 
@@ -107,6 +129,9 @@ soft_reset:
     mp_cstack_init_with_sp_here(CONFIG_MAIN_STACK_SIZE);
     #if MICROPY_ENABLE_GC
     gc_init(heap, heap + sizeof(heap));
+    #if MICROPY_GC_SPLIT_HEAP && DT_HAS_COMPAT_STATUS_OKAY(micropython_heap)
+    DT_FOREACH_STATUS_OKAY(micropython_heap, MICROPY_HEAP_ADD)
+    #endif
     #endif
     mp_init();
 

ports/zephyr/mpconfigport.h

@@ -151,6 +151,10 @@ void mp_hal_signal_event(void);
 #define MICROPY_PY_MACHINE_ADC_READ_UV (1)
 #endif
 
+#if DT_HAS_COMPAT_STATUS_OKAY(micropython_heap)
+#define MICROPY_GC_SPLIT_HEAP (1)
+#endif
+
 typedef long mp_off_t;
 
 #define MP_STATE_PORT MP_STATE_VM