ASoC: dt-bindings: qcom: Document "aux-devs" property

In some cases we need to probe additional audio components that do
not appear as part of the DAI links specified in the device tree.
Examples for this are auxiliary devices such as analog amplifiers
or codecs.

To make them work they need to be added as part of "aux-devs"
and connected to some other audio component using the audio routes
configurable using "(qcom,)audio-routing".

Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200826095141.94017-2-stephan@gerhold.net
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/qcom,apq8016-sbc.txt

@@ -34,6 +34,13 @@ Required properties:
 			  * DMIC
 			  * Ext Spk
 
+Optional properties:
+
+- aux-devs		: A list of phandles for auxiliary devices (e.g. analog
+			  amplifiers) that do not appear directly within the DAI
+			  links. Should be connected to another audio component
+			  using "qcom,audio-routing".
+
 Dai-link subnode properties and subnodes:
 
 Required dai-link subnodes:

Documentation/devicetree/bindings/sound/qcom,apq8096.txt

@@ -55,6 +55,14 @@ This binding describes the APQ8096 sound card, which uses qdsp for audio.
 	Value type: <stringlist>
 	Definition: The user-visible name of this sound card.
 
+- aux-devs
+	Usage: optional
+	Value type: <array of phandles>
+	Definition: A list of phandles for auxiliary devices (e.g. analog
+		    amplifiers) that do not appear directly within the DAI
+		    links. Should be connected to another audio component
+		    using "audio-routing".
+
 = dailinks
 Each subnode of sndcard represents either a dailink, and subnodes of each
 dailinks would be cpu/codec/platform dais.

Documentation/devicetree/bindings/sound/qcom,sdm845.txt

@@ -24,6 +24,14 @@ This binding describes the SDM845 sound card, which uses qdsp for audio.
 	Value type: <stringlist>
 	Definition: The user-visible name of this sound card.
 
+- aux-devs
+	Usage: optional
+	Value type: <array of phandles>
+	Definition: A list of phandles for auxiliary devices (e.g. analog
+		    amplifiers) that do not appear directly within the DAI
+		    links. Should be connected to another audio component
+		    using "audio-routing".
+
 = dailinks
 Each subnode of sndcard represents either a dailink, and subnodes of each
 dailinks would be cpu/codec/platform dais.