intel_debug: introduction: Add information about modular SOF release content

The firmware supports library loading starting with Meteor Lake and the
release system is prepared to offer modular SOF releases.

Update the documentation of the SOF release content to reflect this.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

Author: ujfalusi

getting_started/intel_debug/introduction.rst

@@ -94,7 +94,10 @@ User space and filesystem requirements
 Selecting the SOF driver is not enough. Audio is properly configured only if
 the following elements are present on the file system.
 
-1. Firmware binary
+1. Firmware
+-----------
+
+1.1. Base firmware
 ------------------
 
 The firmware file, ``/lib/firmware/intel/sof/sof-tgl.ri`` (example
@@ -117,6 +120,46 @@ Linux kernel to query whether or not the firmware authentication is enabled,
 which means `dmesg` logs cannot be provided to alert the user to an ME
 configuration issue.
 
+.. _loadable-libraries:
+
+1.2. Loadable libraries
+-----------------------
+
+An IPC4 library is a container of a single or multiple modules (bundle) which
+can be loaded to the firmware after it is booted up.
+Library loading is  supported on Meteor Lake (ACE1) or newer platforms.
+
+Background information: the base firmware always resides in DSP SRAM while the
+loaded library is stored in DRAM memory and only the needed code is copied to
+SRAM for execution. By moving modules out from the base firmware to a library
+can reduce the overall SRAM use depending on the device configuration and
+topology.
+
+See :ref:`llext_modules` for technical details.
+
+1.3. Monolithic and modular SOF releases
+----------------------------------------
+
+SOF project releases for Intel platforms are either monolithic (only a single firmware binary) or modular (base firmware and external libraries).
+
+1.3.1. Modular SOF releases
+---------------------------
+
+See :ref:`loadable-libraries` for details about library support in general.
+
+The released libraries are:
+ - **sof-PLAT-openmodules.ri** : the bundle contains modules for audio processing not included in the base firmware
+ - **sof-PLAT-debug.ri** : the bundle contains modules that are needed for firmware debugging and profiling. Used by developers and for bug reporting if needed
+ - **UUID.bin** : Mainly 3rd party libraries identified by UUID. If the library contains multiple modules then a UUID symlink must be provided for each one.
+
+Notes:
+ - The Kernel will attempt to load \*-openmodules.ri followed by \*-debug.ri from the library path after the base firmware boot if they exist.
+ - additional libraries referenced by topology files or drivers will be loaded based on the UUID of the module from the library path.
+
+
+1.4 Firmware lookup paths
+-------------------------
+
 Linux SOF will look up firmware files at the following paths:
 
 .. _intel_firmware_paths:
@@ -144,14 +187,14 @@ Linux SOF will look up firmware files at the following paths:
      - IPC4
      - /lib/firmware/intel/sof-ipc4/PLAT/community/sof-PLAT.ri
      - PLAT = tgl, adl, rpl, mtl, lnl, ...
-   * - Tiger Lake and newer Loadable Module
+   * - Meteor Lake and newer Loadable libraries
      - IPC4
-     - /lib/firmware/intel/sof-ipc4-lib/PLAT/UUID.bin
-     - PLAT as above, UUID = UUID of the module
-   * - Tiger Lake and newer Loadable Module (community signed)
+     - /lib/firmware/intel/sof-ipc4-lib/PLAT/
+     - PLAT = mtl, lnl, ...
+   * - Meteor Lake and newer Loadable libraries (community signed)
      - IPC4
-     - /lib/firmware/intel/sof-ipc4-lib/PLAT/community/UUID.bin
-     - PLAT as above, UUID = UUID of the module
+     - /lib/firmware/intel/sof-ipc4-lib/PLAT/community/
+     - PLAT = mtl, lnl, ...
 
 Important notices:
  - The standard Linux firmware search path and order is followed. The above table covers the base "/lib/firmware" case. See https://docs.kernel.org/driver-api/firmware/fw_search_path.html for more information.