ASoC: codecs: tlv320aic3x: add SPI to the DT binding

Added note and example of SPI support.
Signed-off-by: Jiri Prchal <jiri.prchal@aksignal.cz>
Link: https://lore.kernel.org/r/20210408060741.6879-1-jiri.prchal@aksignal.czSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/tlv320aic3x.txt

 Texas Instruments - tlv320aic3x Codec module
 
-The tlv320aic3x serial control bus communicates through I2C protocols
+The tlv320aic3x serial control bus communicates through both I2C and SPI bus protocols
 
 Required properties:
 
@@ -63,7 +63,7 @@ CODEC input pins for other compatible codecs:
 
 The pins can be used in referring sound node's audio-routing property.
 
-Example:
+I2C example:
 
 #include <dt-bindings/gpio/gpio.h>
 
@@ -78,3 +78,20 @@ tlv320aic3x: tlv320aic3x@1b {
 	DRVDD-supply = <&regulator>;
 	DVDD-supply = <&regulator>;
 };
+
+SPI example:
+
+spi0: spi@f0000000 {
+	tlv320aic3x: codec@0 {
+		compatible = "ti,tlv320aic3x";
+		reg = <0>; /* CS number */
+		#sound-dai-cells = <0>;
+		spi-max-frequency = <1000000>;
+
+		AVDD-supply = <&regulator>;
+		IOVDD-supply = <&regulator>;
+		DRVDD-supply = <&regulator>;
+		DVDD-supply = <&regulator>;
+		ai3x-ocmv = <0>;
+	};
+};