dt-bindings: mfd: motorola-cpcap: Document audio-codec

This adds the DT binding for the audio-codec sub-module found
inside the Motorola CPCAP PMIC.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/motorola-cpcap.txt

@@ -12,6 +12,30 @@ Required properties:
 - spi-max-frequency	: Typically set to 3000000
 - spi-cs-high		: SPI chip select direction
 
+Optional subnodes:
+
+The sub-functions of CPCAP get their own node with their own compatible values,
+which are described in the following files:
+
+- ../power/supply/cpcap-battery.txt
+- ../power/supply/cpcap-charger.txt
+- ../regulator/cpcap-regulator.txt
+- ../phy/phy-cpcap-usb.txt
+- ../input/cpcap-pwrbutton.txt
+- ../rtc/cpcap-rtc.txt
+- ../leds/leds-cpcap.txt
+- ../iio/adc/cpcap-adc.txt
+
+The only exception is the audio codec. Instead of a compatible value its
+node must be named "audio-codec".
+
+Required properties for the audio-codec subnode:
+
+- #sound-dai-cells = <1>;
+
+The audio-codec provides two DAIs. The first one is connected to the
+Stereo HiFi DAC and the second one is connected to the Voice DAC.
+
 Example:
 
 &mcspi1 {
@@ -26,6 +50,24 @@ Example:
 		#size-cells = <0>;
 		spi-max-frequency = <3000000>;
 		spi-cs-high;
+
+		audio-codec {
+			#sound-dai-cells = <1>;
+
+			/* HiFi */
+			port@0 {
+				endpoint {
+					remote-endpoint = <&cpu_dai1>;
+				};
+			};
+
+			/* Voice */
+			port@1 {
+				endpoint {
+					remote-endpoint = <&cpu_dai2>;
+				};
+			};
+		};
 	};
 };