[nrf fromtree] devicetree: Fix MTD macro for subpartitions

The DT_MTD_FROM_FIXED_SUBPARTITION must go one level more than the
DT_MTD_FROM_FIXED_PARTITION counterpart.

Signed-off-by: Tomasz Chyrowicz <[email protected]>
(cherry picked from commit e4ecd4b)

Author: tomchy

include/zephyr/devicetree/fixed-partitions.h

@@ -160,7 +160,7 @@ extern "C" {
  */
 #define DT_MTD_FROM_FIXED_SUBPARTITION(node_id)                                                    \
 	COND_CODE_1(DT_NODE_EXISTS(DT_MEM_FROM_FIXED_SUBPARTITION(node_id)),                       \
-		    (DT_PARENT(DT_MEM_FROM_FIXED_SUBPARTITION(node_id))), (DT_GPARENT(node_id)))
+	     (DT_PARENT(DT_MEM_FROM_FIXED_SUBPARTITION(node_id))), (DT_GPARENT(DT_PARENT(node_id))))
 
 /**
  * @brief Get the absolute address of a fixed subpartition

tests/lib/devicetree/api/src/main.c

@@ -3312,6 +3312,9 @@ ZTEST(devicetree_api, test_fixed_subpartitions)
 	zassert_true(DT_NODE_EXISTS(DT_MTD_FROM_FIXED_PARTITION(TEST_SUBPARTITION_COMBINED)));
 	zassert_true(DT_NODE_EXISTS(DT_MTD_FROM_FIXED_SUBPARTITION(TEST_SUBPARTITION_0)));
 	zassert_true(DT_NODE_EXISTS(DT_MTD_FROM_FIXED_SUBPARTITION(TEST_SUBPARTITION_1)));
+	zassert_true(DT_SAME_NODE(
+		DT_MTD_FROM_FIXED_PARTITION(TEST_SUBPARTITION_COMBINED),
+		DT_MTD_FROM_FIXED_SUBPARTITION(TEST_SUBPARTITION_1)));
 
 	/* Test DT_FIXED_SUBPARTITION_ADDR. */
 	zassert_equal(DT_FIXED_PARTITION_ADDR(TEST_SUBPARTITION_COMBINED), 0x20000100);