Document the Qualcomm WCD9390/WCD9395 USB SubSystem Altmode/Analog Audio Switch
which is a separate USB SubSystem for Altmode/Analog Audio Switch accessible
over an I2C interface.

Since Audio Headphone and Microphone data path between the Codec and the USB-C Mux
subsystems are external to the IC, it requires a second port to handle USB-C altmode
& orientation switching for Audio Accessory Mode to the Codec SubSystem.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231212-topic-sm8650-upstream-wcd939x-usbss-v2-1-38961fea5867@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>