dt-bindings: iio: document dpot-dac bindings

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/dac/dpot-dac.txt

+Bindings for DAC emulation using a digital potentiometer
+
+It is assumed that the dpot is used as a voltage divider between the
+current dpot wiper setting and the maximum resistance of the dpot. The
+divided voltage is provided by a vref regulator.
+
+                  .------.
+   .-----------.  |      |
+   | vref      |--'    .---.
+   | regulator |--.    |   |
+   '-----------'  |    | d |
+                  |    | p |
+                  |    | o |  wiper
+                  |    | t |<---------+
+                  |    |   |
+                  |    '---'       dac output voltage
+                  |      |
+                  '------+------------+
+
+Required properties:
+- compatible: Should be "dpot-dac"
+- vref-supply: The regulator supplying the voltage divider.
+- io-channels: Channel node of the dpot to be used for the voltage division.
+- io-channel-names: Should be "dpot".
+
+Example:
+
+	&i2c {
+		dpot: mcp4651-503@28 {
+			compatible = "microchip,mcp4651-503";
+			reg = <0x28>;
+			#io-channel-cells = <1>;
+		};
+	};
+
+	dac {
+		compatible = "dpot-dac";
+		vref-supply = <&reg_3v3>;
+		io-channels = <&dpot 0>;
+		io-channel-names = "dpot";
+	};

MAINTAINERS

@@ -6119,6 +6119,12 @@ L:	linux-media@vger.kernel.org
 S:	Maintained
 F:	drivers/media/rc/iguanair.c
 
+IIO DIGITAL POTENTIOMETER DAC
+M:	Peter Rosin <peda@axentia.se>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/dac/dpot-dac.txt
+
 IIO SUBSYSTEM AND DRIVERS
 M:	Jonathan Cameron <jic23@kernel.org>
 R:	Hartmut Knaack <knaack.h@gmx.de>