clk: samsung: Document binding for Exynos4415 clock controller

This patch adds DT binding documentation for Exynos4415 SoC system
clock controllers.
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

Documentation/devicetree/bindings/clock/exynos4415-clock.txt

+* Samsung Exynos4415 Clock Controller
+
+The Exynos4415 clock controller generates and supplies clock to various
+consumer devices within the Exynos4415 SoC.
+
+Required properties:
+
+- compatible: should be one of the following:
+  - "samsung,exynos4415-cmu" - for the main system clocks controller
+    (CMU_LEFTBUS, CMU_RIGHTBUS, CMU_TOP, CMU_CPU clock domains).
+  - "samsung,exynos4415-cmu-dmc" - for the Exynos4415 SoC DRAM Memory
+    Controller (DMC) domain clock controller.
+
+- reg: physical base address of the controller and length of memory mapped
+  region.
+
+- #clock-cells: should be 1.
+
+Each clock is assigned an identifier and client nodes can use this identifier
+to specify the clock which they consume.
+
+All available clocks are defined as preprocessor macros in
+dt-bindings/clock/exynos4415.h header and can be used in device
+tree sources.
+
+Example 1: An example of a clock controller node is listed below.
+
+	cmu: clock-controller@10030000 {
+		compatible = "samsung,exynos4415-cmu";
+		reg = <0x10030000 0x18000>;
+		#clock-cells = <1>;
+	};
+
+	cmu-dmc: clock-controller@105C0000 {
+		compatible = "samsung,exynos4415-cmu-dmc";
+		reg = <0x105C0000 0x3000>;
+		#clock-cells = <1>;
+	};