doc: Update migration guide - New Serial BUS implementation

Add migration guide for PAL serial BUS for nRF52840.

Signed-off-by: Marcin Gasiorek <[email protected]>

doc/releases_and_migration/migration_guide_v280.rst

@@ -7,54 +7,12 @@ Migration guide for the v2.8.0 of the nRF Connect SDK
    :local:
    :depth: 2
 
-Starting with the v2.8.0 release of the `nRF Connect SDK`_, there is a new Sidewalk provisioning module.
-For an overview of changes, read the following sections.
+Starting with the v2.8.0 release of the `nRF Connect SDK`_, there are new Sidewalk provisioning module and PAL serial bus for nRF52840 SoC.
+For an overview of changes, read the following sections:
 
-Reasons for change
-==================
+.. toctree::
+   :maxdepth: 1
+   :glob:
 
-The new provisioning module enhances security by:
-
-* Moving non-volatile Sidewalk keys to secure key storage.
-* Protecting the manufacturing data partition from write operations.
-* Always using the Key-Value Store version of manufacturing data.
-
-Security enhancements details
-=============================
-
-Access to the manufacturing data is unified within the application, ensuring consistency for prototyping and manufacturing flows.
-The MFG parser module is launched at initialization and writes the manufacturing data to flash (secure key storage) in the same way as the device certification module.
-The process is triggered only once, at the first application start after flashing the :file:`Nordic_MFG.hex` file.
-The following logs are generated:
-
-.. code-block:: console
-
-   [00:00:00.004,502] <inf> sid_mfg: Need to parse mfg data
-   [00:00:00.009,993] <inf> sid_mfg_parser_v8: MFG_ED25519 import success
-   [00:00:00.014,900] <inf> sid_mfg_parser_v8: MFG_SECP_256R1 import success
-   [00:00:00.054,505] <inf> sid_mfg: Successfully parsed mfg data
-
-The secure key storage is based on the `Hardware unique key`_ security library.
-After keys are imported into secure key storage, it is impossible to read their raw values.
-Therefore, once secure key storage is enabled in the firmware, it must remain enabled in all subsequent firmware versions. 
-This feature is enabled by default in all Sidewalk samples.
-
-The hardware flash write protection is based on the `Hardware flash write protection`_ security library.
-The protection is applied during Sidewalk initialization and remains irreversible until reset.
-This feature is disabled in the :ref:`variant_sidewalk_dut` sample to allow writing of manufacturing data using on-device certification commands.
-
-Aligning your application to the new model
-==========================================
-
-The new provisioning module implementation includes the following changes:
-
-* In the :file:`app_mfg_config.h` file, the function ``app_mfg_cfg_is_valid()`` was renamed to ``app_mfg_cfg_is_empty()``.
-
-* The ``CONFIG_SIDEWALK_MFG_STORAGE_SUPPORT_HEX_v7`` Kconfig option adds support for older Sidewalk manufacturing HEX formats (version 7 and below). 
-  You can disable this configuration when using the latest manufacturing flash.
-
-Using old provisioning module
-=============================
-
-It is recommended to use the new provisioning module implementation. 
-However, you can still enable the old module using the ``CONFIG_DEPRECATED_SIDEWALK_MFG_STORAGE`` Kconfig option. 
+   migration_guide_v280_provisioning_module.rst
+   migration_guide_v280_serial_bus.rst

doc/releases_and_migration/migration_guide_v280_provisioning_module.rst

@@ -0,0 +1,53 @@
+.. _migration_guide_v280_prov_module:
+
+Sidewalk provisioning module
+****************************
+
+Reasons for change
+==================
+
+The new provisioning module enhances security by:
+
+* Moving non-volatile Sidewalk keys to secure key storage.
+* Protecting the manufacturing data partition from write operations.
+* Always using the Key-Value Store version of manufacturing data.
+
+Security enhancements details
+=============================
+
+Access to the manufacturing data is unified within the application, ensuring consistency for prototyping and manufacturing flows.
+The MFG parser module is launched at initialization and writes the manufacturing data to flash (secure key storage) in the same way as the device certification module.
+The process is triggered only once, at the first application start after flashing the :file:`Nordic_MFG.hex` file.
+The following logs are generated:
+
+.. code-block:: console
+
+   [00:00:00.004,502] <inf> sid_mfg: Need to parse mfg data
+   [00:00:00.009,993] <inf> sid_mfg_parser_v8: MFG_ED25519 import success
+   [00:00:00.014,900] <inf> sid_mfg_parser_v8: MFG_SECP_256R1 import success
+   [00:00:00.054,505] <inf> sid_mfg: Successfully parsed mfg data
+
+The secure key storage is based on the `Hardware unique key`_ security library.
+After keys are imported into secure key storage, it is impossible to read their raw values.
+Therefore, once secure key storage is enabled in the firmware, it must remain enabled in all subsequent firmware versions. 
+This feature is enabled by default in all Sidewalk samples.
+
+The hardware flash write protection is based on the `Hardware flash write protection`_ security library.
+The protection is applied during Sidewalk initialization and remains irreversible until reset.
+This feature is disabled in the :ref:`variant_sidewalk_dut` sample to allow writing of manufacturing data using on-device certification commands.
+
+Aligning your application to the new model
+==========================================
+
+The new provisioning module implementation includes the following changes:
+
+* In the :file:`app_mfg_config.h` file, the function ``app_mfg_cfg_is_valid()`` was renamed to ``app_mfg_cfg_is_empty()``.
+
+* The ``CONFIG_SIDEWALK_MFG_STORAGE_SUPPORT_HEX_v7`` Kconfig option adds support for older Sidewalk manufacturing HEX formats (version 7 and below). 
+  You can disable this configuration when using the latest manufacturing flash.
+
+Using old provisioning module
+=============================
+
+It is recommended to use the new provisioning module implementation. 
+However, you can still enable the old module using the ``CONFIG_DEPRECATED_SIDEWALK_MFG_STORAGE`` Kconfig option. 

doc/releases_and_migration/migration_guide_v280_serial_bus.rst

@@ -0,0 +1,28 @@
+.. _migration_guide_v280_serial_bus:
+
+Sidewalk PAL serial bus for nRF52840 SoC
+****************************************
+
+Reasons for change
+==================
+
+Due to fact that Zephyr's SPI driver adds additional delay to the SPI bus communication, which have significant impact to the
+FSK protocol for nRF52840, hence the new implementation of the PAL serial bus is introduced.
+
+Aligning your application to the new PAL serial bus
+===================================================
+
+The new PAL serial bus implementation includes the following changes:
+
+* Added the :file:`sid_pal_serial_bus_nrfx_spi.c` file with the PAL SPI bus implementation based on the NRFX SPI driver.
+  This PAL is used only for nRF52840 SoC build and it has no impact to other platforms.
+
+* The new ``CONFIG_SIDEWALK_NRFX_SPI_INSTANCE_ID`` Kconfig option for selecting SPI bus instance for communication with an external
+  sub-GHz transceiver.
+
+* Added the ``nrfx_spi_gpios`` child node in the :file:`nrf52840dk_nrf52840.overlay` overlay for configuring the
+  SPI bus ``CLK``, ``MOSI``, ``MISO`` and ``CS`` pins.
+
+  .. note::
+    When SPI bus instance is selected by ``CONFIG_SIDEWALK_NRFX_SPI_INSTANCE_ID`` Kconfig option, it is strongly recommended
+    to disable it in the devicetree.