ARM: dts: thermal: exynos: Add documentation for Exynos SoC thermal bindings

* Exynos Thermal Management Unit (TMU)

** Required properties:

- compatible : One of the following:

	       "samsung,exynos4412-tmu"

	       "samsung,exynos4210-tmu"

	       "samsung,exynos5250-tmu"

	       "samsung,exynos5440-tmu"

- interrupt-parent : The phandle for the interrupt controller

- reg : Address range of the thermal registers. For soc's which has multiple

	instances of TMU and some registers are shared across all TMU's like

	interrupt related then 2 set of register has to supplied. First set

	belongs	to each instance of TMU and second set belongs to common TMU

	registers.

- interrupts : Should contain interrupt for thermal system

- clocks : The main clock for TMU device

- clock-names : Thermal system clock name

- vtmu-supply: This entry is optional and provides the regulator node supplying

		voltage to TMU. If needed this entry can be placed inside

		board/platform specific dts file.

Example 1):

	tmu@100C0000 {

		compatible = "samsung,exynos4412-tmu";

		interrupt-parent = <&combiner>;

		reg = <0x100C0000 0x100>;

		interrupts = <2 4>;

		clocks = <&clock 383>;

		clock-names = "tmu_apbif";

		status = "disabled";

		vtmu-supply = <&tmu_regulator_node>;

	};

Example 2):

	tmuctrl_0: tmuctrl@160118 {

		compatible = "samsung,exynos5440-tmu";

		reg = <0x160118 0x230>, <0x160368 0x10>;

		interrupts = <0 58 0>;

		clocks = <&clock 21>;

		clock-names = "tmu_apbif";

	};

Note: For multi-instance tmu each instance should have an alias correctly

numbered in "aliases" node.

Example:

aliases {

	tmuctrl0 = &tmuctrl_0;

	tmuctrl1 = &tmuctrl_1;

	tmuctrl2 = &tmuctrl_2;

};