dt-bindings: auxadc: Add binding document for Mediatek auxadc.

The commit adds the device tree binding documentation for the mediatek
auxadc found on Mediatek MT2701.
Thermal gets auxadc sample data by iio device.
So the commit changes auxadc device tree binding documentation from
/soc/mediatek/auxadc.txt to /iio/adc/mt6577_auxadc.txt.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Zhiyong Tao <zhiyong.tao@mediatek.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/adc/mt6577_auxadc.txt

@@ -0,0 +1,29 @@
+* Mediatek AUXADC - Analog to Digital Converter on Mediatek mobile soc (mt65xx/mt81xx/mt27xx)
+===============
+
+The Auxiliary Analog/Digital Converter (AUXADC) is an ADC found
+in some Mediatek SoCs which among other things measures the temperatures
+in the SoC. It can be used directly with register accesses, but it is also
+used by thermal controller which reads the temperatures from the AUXADC
+directly via its own bus interface. See
+Documentation/devicetree/bindings/thermal/mediatek-thermal.txt
+for the Thermal Controller which holds a phandle to the AUXADC.
+
+Required properties:
+  - compatible: Should be one of:
+    - "mediatek,mt2701-auxadc": For MT2701 family of SoCs
+    - "mediatek,mt8173-auxadc": For MT8173 family of SoCs
+  - reg: Address range of the AUXADC unit.
+  - clocks: Should contain a clock specifier for each entry in clock-names
+  - clock-names: Should contain "main".
+  - #io-channel-cells: Should be 1, see ../iio-bindings.txt
+
+Example:
+
+auxadc: adc@11001000 {
+	compatible = "mediatek,mt2701-auxadc";
+	reg = <0 0x11001000 0 0x1000>;
+	clocks = <&pericfg CLK_PERI_AUXADC>;
+	clock-names = "main";
+	#io-channel-cells = <1>;
+};

Documentation/devicetree/bindings/soc/mediatek/auxadc.txt

@@ -1,21 +0,0 @@
-MediaTek AUXADC
-===============
-
-The Auxiliary Analog/Digital Converter (AUXADC) is an ADC found
-in some Mediatek SoCs which among other things measures the temperatures
-in the SoC. It can be used directly with register accesses, but it is also
-used by thermal controller which reads the temperatures from the AUXADC
-directly via its own bus interface. See
-Documentation/devicetree/bindings/thermal/mediatek-thermal.txt
-for the Thermal Controller which holds a phandle to the AUXADC.
-
-Required properties:
-- compatible: Must be "mediatek,mt8173-auxadc"
-- reg: Address range of the AUXADC unit
-
-Example:
-
-auxadc: auxadc@11001000 {
-	compatible = "mediatek,mt8173-auxadc";
-	reg = <0 0x11001000 0 0x1000>;
-};