ASoC: samsung: Document Odroid X2/U3 audio subsystem bindings

Signed-off-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/sound/samsung,odroidx2-max98090.txt

+Samsung Exynos Odroid X2/U3 audio complex with MAX98090 codec
+
+Required properties:
+ - compatible : "samsung,odroidx2-audio" - for Odroid X2 board,
+		"samsung,odroidu3-audio" - for Odroid U3 board
+ - samsung,model : the user-visible name of this sound complex
+ - samsung,i2s-controller : the phandle of the I2S controller
+ - samsung,audio-codec : the phandle of the MAX98090 audio codec
+ - samsung,audio-routing : a list of the connections between audio
+   components;  each entry is a pair of strings, the first being the
+   connection's sink, the second being the connection's source;
+   valid names for sources and sinks are the MAX98090's pins (as
+   documented in its binding), and the jacks on the board
+   For Odroid X2:
+     * Headphone Jack
+     * Mic Jack
+     * DMIC
+
+   For Odroid U3:
+     * Headphone Jack
+     * Speakers
+
+Example:
+
+sound {
+	compatible = "samsung,odroidu3-audio";
+	samsung,i2s-controller = <&i2s0>;
+	samsung,audio-codec = <&max98090>;
+	samsung,model = "Odroid-X2";
+	samsung,audio-routing =
+		"Headphone Jack", "HPL",
+		"Headphone Jack", "HPR",
+		"IN1", "Mic Jack",
+		"Mic Jack", "MICBIAS";
+};