clk: max77802: Add DT binding documentation

Add Device Tree binding documentation for the clocks
outputs in the Maxim 77802 Power Management IC.
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

Documentation/devicetree/bindings/clock/maxim,max77802.txt

+Binding for Maxim MAX77802 32k clock generator block
+
+This is a part of device tree bindings of MAX77802 multi-function device.
+More information can be found in bindings/mfd/max77802.txt file.
+
+The MAX77802 contains two 32.768khz clock outputs that can be controlled
+(gated/ungated) over I2C.
+
+Following properties should be present in main device node of the MFD chip.
+
+Required properties:
+- #clock-cells: From common clock binding; shall be set to 1.
+
+Optional properties:
+- clock-output-names: From common clock binding.
+
+Each clock is assigned an identifier and client nodes can use this identifier
+to specify the clock which they consume. Following indices are allowed:
+     - 0: 32khz_ap clock,
+     - 1: 32khz_cp clock.
+
+Clocks are defined as preprocessor macros in dt-bindings/clock/maxim,max77802.h
+header and can be used in device tree sources.
+
+Example: Node of the MFD chip
+
+	max77802: max77802@09 {
+		compatible = "maxim,max77802";
+		interrupt-parent = <&wakeup_eint>;
+		interrupts = <26 0>;
+		reg = <0x09>;
+		#clock-cells = <1>;
+
+		/* ... */
+	};
+
+Example: Clock consumer node
+
+	foo@0 {
+		compatible = "bar,foo";
+		/* ... */
+		clock-names = "my-clock";
+		clocks = <&max77802 MAX77802_CLK_32K_AP>;
+	};