ASoC: qcom: Document LPASS CPU bindings

Add documentation to the sound directory of the
device-tree bindings for the QTi LPASS CPU DAI
device.
Signed-off-by: Kenneth Westfield <kwestfie@codeaurora.org>
Acked-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/qcom,lpass-cpu.txt

+* Qualcomm Technologies LPASS CPU DAI
+
+This node models the Qualcomm Technologies Low-Power Audio SubSystem (LPASS).
+
+Required properties:
+
+- compatible		: "qcom,lpass-cpu"
+- clocks		: Must contain an entry for each entry in clock-names.
+- clock-names		: A list which must include the following entries:
+				* "ahbix-clk"
+				* "mi2s-osr-clk"
+				* "mi2s-bit-clk"
+- interrupts		: Must contain an entry for each entry in
+			  interrupt-names.
+- interrupt-names	: A list which must include the following entries:
+				* "lpass-irq-lpaif"
+- pinctrl-N		: One property must exist for each entry in
+			  pinctrl-names.  See ../pinctrl/pinctrl-bindings.txt
+			  for details of the property values.
+- pinctrl-names		: Must contain a "default" entry.
+- reg			: Must contain an address for each entry in reg-names.
+- reg-names		: A list which must include the following entries:
+				* "lpass-lpaif"
+
+Required subnodes:
+
+- qcom,adsp		: Audio DSP sub-node
+
+Optional Audio DSP subnode properties:
+
+- status		: "disabled" indicates the adsp is not available.
+
+Example:
+
+lpass@28100000 {
+	compatible = "qcom,lpass-cpu";
+	clocks = <&lcc AHBIX_CLK>, <&lcc MI2S_OSR_CLK>, <&lcc MI2S_BIT_CLK>;
+	clock-names = "ahbix-clk", "mi2s-osr-clk", "mi2s-bit-clk";
+	interrupts = <0 85 1>;
+	interrupt-names = "lpass-irq-lpaif";
+	pinctrl-names = "default", "idle";
+	pinctrl-0 = <&mi2s_default>;
+	pinctrl-1 = <&mi2s_idle>;
+	reg = <0x28100000 0x10000>;
+	reg-names = "lpass-lpaif";
+	qcom,adsp {
+		status = "disabled";
+	};
+};