arch: fw: sof-zephyr io drivers

sof-zephyr rtos architecture chapter for io drivers

Signed-off-by: Michal Wasko <[email protected]>

Author: mwasko

architectures/firmware/sof-zephyr/rtos_layer/index.rst

@@ -11,3 +11,4 @@ workloads.
    :maxdepth: 1
 
    zephyr_kernel_overview
+   io_drivers/index

architectures/firmware/sof-zephyr/rtos_layer/io_drivers/images/io_drivers_diagram.pu

@@ -0,0 +1,16 @@
+frame "SOF" {
+	component Gateway
+	component GatewayExtension <<type>>
+}
+
+frame "Zephyr" {
+	component IoDriver <<type>>
+	component DMA
+}
+
+Gateway *-right- GatewayExtension
+
+Gateway -down- IoDriver
+Gateway -down- DMA
+
+GatewayExtension ..> IoDriver

architectures/firmware/sof-zephyr/rtos_layer/io_drivers/index.rst

@@ -0,0 +1,21 @@
+.. _io_drivers:
+
+IO Drivers
+##########
+
+The IO Drivers provide access to an IO HW Interfaces connected to the DSP, e.g.
+I2S, DMIC, etc. and are managed as a part of the Zephyr RTOS. The Audio IO
+Drivers share generic `Zephyr DAI interface <https://docs.zephyrproject.org/apidoc/latest/group__dai__interface.html>`__.
+For a full list of IO drivers available on the specific platform, refer to
+:ref:`platforms`. HW IO is accessed via the `Gateway` interface inside the FW.
+The actual implementation of that interface depends on the underlying HW IO
+mechanism. Gateways use the Zephyr DMA interface to transmit the data to/from
+the represented HW IO. DMA interface implementation depends on the underlying
+DMA method (HDA-DMA, GPDMA, etc.).
+
+**NOTE:** The introduction of Gateways concept to SOF with Zephyr is a work in
+progress. In existing implementation the SOF Host and DAI implementation is
+still in use as a substitute of Gateways.
+
+.. uml:: images/io_drivers_diagram.pu
+   :caption: IO Drivers diagram