boards: frdm_rw612: Document SRAM partitions

Add comment to DTS file about SRAM partitions similar to the RTXXX
series has comments.

Add also a doc section to the frdm_rw612 about this.

Also fix the section hierarchy of the frdm_rw612 doc, the header levels
were wrong since the wifi and bluetooth, and reference sections were
under the debugging section.
Group all the wireless connectivity info together.

Signed-off-by: Declan Snyder <[email protected]>

Author: decsny

boards/nxp/frdm_rw612/doc/index.rst

@@ -76,16 +76,6 @@ The default configuration can be found in the defconfig file:
 
 Other hardware features are not currently supported
 
-Fetch Binary Blobs
-******************
-
-To support Bluetooth or Wi-Fi, frdm_rw612 requires fetching binary blobs, which can be
-achieved by running the following command:
-
-.. code-block:: console
-
-   west blobs fetch hal_nxp
-
 Programming and Debugging
 *************************
 
@@ -147,6 +137,34 @@ should see the following message in the terminal:
    ***** Booting Zephyr OS zephyr-v3.6.0 *****
    Hello World! frdm_rw612
 
+SRAM Bus Access Partitioning
+****************************
+
+RW612 supports shared access of the SRAM from both the code bus and data bus.
+The bus used to access the SRAM is determined using two separate memory mapped address spaces.
+The application can configure the partitioning of the SRAM access regions by a devicetree overlay.
+For example, below is part of an overlay to change the whole SRAM to be used for data.
+
+.. code-block:: devicetree
+
+   &sram_data {
+        reg = <0x0 DT_SIZE_K(1216)>;
+   };
+
+
+Wireless Connectivity Support
+*****************************
+
+Fetch Binary Blobs
+==================
+
+To support Bluetooth or Wi-Fi, frdm_rw612 requires fetching binary blobs, which can be
+achieved by running the following command:
+
+.. code-block:: console
+
+   west blobs fetch hal_nxp
+
 Bluetooth
 =========
 
@@ -168,7 +186,7 @@ frdm_rw612 platform supports the monolithic feature. The required binary blob
 with the application image directly, forming one single monolithic image.
 
 Resources
-=========
+*********
 
 .. _RW612 Website:
    https://www.nxp.com/products/wireless-connectivity/wi-fi-plus-bluetooth-plus-802-15-4/wireless-mcu-with-integrated-tri-radiobr1x1-wi-fi-6-plus-bluetooth-low-energy-5-3-802-15-4:RW612

dts/arm/nxp/nxp_rw6xx_common.dtsi

@@ -75,6 +75,11 @@
 	#address-cells = <1>;
 	#size-cells = <1>;
 
+	/* RW6XX SRAM can be access by either code or data bus, determined
+	 * by the address used to access the memory.
+	 * Applications can override the reg properties of either
+	 * sram_data or sram_code nodes to change the balance of SRAM access partitioning.
+	 */
 	sram_data: memory@40000 {
 		compatible = "mmio-sram";
 		reg = <0x40000 DT_SIZE_K(960)>;