dt-bindings: Document the hi6220 thermal sensor bindings

This adds documentation of device tree bindings for the
thermal sensor controller of hi6220 SoC.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: kongxinwei <kong.kongxinwei@hisilicon.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Documentation/devicetree/bindings/thermal/hisilicon-thermal.txt

+* Temperature Sensor on hisilicon SoCs
+
+** Required properties :
+
+- compatible: "hisilicon,tsensor".
+- reg: physical base address of thermal sensor and length of memory mapped
+  region.
+- interrupt: The interrupt number to the cpu. Defines the interrupt used
+  by /SOCTHERM/tsensor.
+- clock-names: Input clock name, should be 'thermal_clk'.
+- clocks: phandles for clock specified in "clock-names" property.
+- #thermal-sensor-cells: Should be 1. See ./thermal.txt for a description.
+
+Example :
+
+	tsensor: tsensor@0,f7030700 {
+		compatible = "hisilicon,tsensor";
+		reg = <0x0 0xf7030700 0x0 0x1000>;
+		interrupts = <0 7 0x4>;
+		clocks = <&sys_ctrl HI6220_TSENSOR_CLK>;
+		clock-names = "thermal_clk";
+		#thermal-sensor-cells = <1>;
+	}