Document the Qualcomm WCD9390/WCD9395 Audio Codec and the
Soundwire devices than can be found on Qualcomm SM8650 based platforms.

The Qualcomm WCD9390/WCD9395 Audio Codec communicates
with the host SoC over 2 Soundwire links to provide:
- 4 ADC inputs for up to 5 Analog Microphones
- 4 DMIC inputs for up to 8 Digital Microphones
- 4 Microphone BIAS
- Stereo Headphone output
- Mono EAR output
- MBHC engine for Headset Detection

The WCD9390/WCD9395 IC has separate I2C subsystem for USB-C
DP Altmode/Audio Accessory mode Mux which is not documented
here but requires port/endpoint graph and properties to handle
Altmode/Audio Accessory switch and orientation.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://msgid.link/r/20231219-topic-sm8650-upstream-wcd939x-codec-v4-2-1c3bbff2d7ab@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>