Pull request project-chip#1755: OTA documentation update

Merge in WMN_TOOLS/matter from ota_doc_updates to RC_2.3.0-1.3

Squashed commit of the following:

commit 5a424081597806b9d54aac6474662dbe38a462d6
Author: Michael Rupp <michael.rupp@silabs.com>
Date:   Fri Apr 19 12:21:46 2024 -0400

    review comment, add section to create encrypted .ota

commit 8094896d93b304979257c8297e1a24639784cf34
Author: Michael Rupp <michael.rupp@silabs.com>
Date:   Sat Apr 13 11:58:32 2024 -0400

    OTA documentation update

Author: mykrupp

docs/silabs/general/OTA_SOFTWARE_UPDATE.md

@@ -280,6 +280,20 @@ Host will initiate OTA download to receive combined image (TA+M4) and store M4 a
     ```
 - The application device will connect to the Provider and start the image download. Once the image is downloaded the device will reboot into the downloaded image.
 
+## Multi-Chip OTA Images
+Multi-Chip OTA is implemented only for EFR32 devices. Multi-chip OTA uses an enhanced ota_image_tool.py script which creates .ota files that contain additional TLV headers. These TLV headers describe the binaries to be sent over the air. The enhanced script is located at scripts/tool/silabs/ota/ota_image_tool.py which is a wrapper to the original src/app/ota_image_tool.py. Multiple binaries can be packaged in the .ota file. Some Tags are reserved for specific Silicon Labs binaries, and other Tags are available to be used for arbitrary TLVs. The payloads can be encrypted. 
+
+For more information on creating a Multi-Chip .ota file see the 
+[README.md](https://github.com/SiliconLabs/matter/blob/latest/scripts/tools/silabs/ota/README.md)
+
+OTA-A applications must be built with an additional gn argument to enable them to process the TLVs. 
+
+    ```shell
+    $ ./scripts/examples/gn_silabs_example.sh examples/lighting-app/silabs/ out/lighting-app BRD41xx chip_enable_multi_ota_requestor=true
+    ```
+
+chip_enable_multi_ota_encryption=true should be added to the build command if the requestor is meant to process encrypted payloads.
+
 ## Additional Info
 
 Developers can find more resources on

scripts/tools/silabs/ota/README.md

@@ -25,8 +25,7 @@ python3 ./scripts/tools/silabs/ota/ota_image_tool.py create -v 0xDEAD -p 0xBEEF
 ```
 
 followed by \*_custom options_- and a positional argument (should be last) that
-specifies the output file. Please see the `create_ota_images.sh` for some
-reference commands.
+specifies the output file.
 
 The list of **custom options**:
 
@@ -38,19 +37,17 @@ The list of **custom options**:
 --app-version-str  --> Application version string. Same as above.
 --app-build-date   --> Application build date. Same as above.
 
-# SSBL options
---bl-input-file    --> Path to the SSBL binary.
---bl-version       --> SSBL version.
---bl-version-str   --> SSBL version string.
---bl-build-date    --> SSBL build date.
-
 # Factory data options
 --factory-data     --> If set, enables the generation of factory data.
 --cert_declaration --> Certification Declaration.
 --dac_cert         --> DAC certificate.
 --dac_key          --> DAC private key.
 --pai_cert         --> PAI certificate.
 
+# Encryption options
+--enc_enable       --> Enable ota encryption
+--input_ota_key    --> 16 Byte AES key
+
 # Custom TLV options
 --json             --> Path to a JSON file following ota_payload.schema
 ```
@@ -67,5 +64,5 @@ processing.
 When defining a custom processor, a user is able to also specify the custom
 format of the TLV by creating a JSON file based on the `ota_payload.schema`. The
 tool offers support for describing multiple TLV in the same JSON file. Please
-see the `examples/ota_max_entries_example.json` for a multi-app + SSBL example.
+see the `examples/ota_custom_entries_example.json` for a multi-binary example.
 Option `--json` must be used to specify the path to the JSON file.