dt-bindings: net: bluetooth: Add qualcomm-bluetooth

Add binding document for serial bluetooth chips using Qualcomm protocol.
Signed-off-by: Thierry Escande <thierry.escande@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

Documentation/devicetree/bindings/net/qualcomm-bluetooth.txt

+Qualcomm Bluetooth Chips
+---------------------
+
+This documents the binding structure and common properties for serial
+attached Qualcomm devices.
+
+Serial attached Qualcomm devices shall be a child node of the host UART
+device the slave device is attached to.
+
+Required properties:
+ - compatible: should contain one of the following:
+   * "qcom,qca6174-bt"
+
+Optional properties:
+ - enable-gpios: gpio specifier used to enable chip
+ - clocks: clock provided to the controller (SUSCLK_32KHZ)
+
+Example:
+
+serial@7570000 {
+	label = "BT-UART";
+	status = "okay";
+
+	bluetooth {
+		compatible = "qcom,qca6174-bt";
+
+		enable-gpios = <&pm8994_gpios 19 GPIO_ACTIVE_HIGH>;
+		clocks = <&divclk4>;
+	};
+};