dt-bindings: iio: adc: Add docs for AD7768-1

Document support for AD7768-1 Analog to Digital Converter.
Signed-off-by: Stefan Popa <stefan.popa@analog.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.txt

+Analog Devices AD7768-1 ADC device driver
+
+Required properties for the AD7768-1:
+
+- compatible: Must be "adi,ad7768-1"
+- reg: SPI chip select number for the device
+- spi-max-frequency: Max SPI frequency to use
+	see: Documentation/devicetree/bindings/spi/spi-bus.txt
+- clocks: phandle to the master clock (mclk)
+	see: Documentation/devicetree/bindings/clock/clock-bindings.txt
+- clock-names: Must be "mclk".
+- interrupts: IRQ line for the ADC
+	see: Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+- vref-supply: vref supply can be used as reference for conversion
+- adi,sync-in-gpios: must be the device tree identifier of the SYNC-IN pin. Enables
+	synchronization of multiple devices that require simultaneous sampling.
+	A pulse is always required if the configuration is changed in any way, for example
+	if the filter decimation rate changes. As the line is active low, it should
+	be marked GPIO_ACTIVE_LOW.
+
+Optional properties:
+
+ - reset-gpios : GPIO spec for the RESET pin. If specified, it will be asserted during
+	driver probe. As the line is active low, it should be marked GPIO_ACTIVE_LOW.
+
+Example:
+
+	adc@0 {
+		compatible = "adi,ad7768-1";
+		reg = <0>;
+		spi-max-frequency = <2000000>;
+		spi-cpol;
+		spi-cpha;
+		vref-supply = <&adc_vref>;
+		interrupts = <25 IRQ_TYPE_EDGE_RISING>;
+		interrupt-parent = <&gpio>;
+		adi,sync-in-gpios = <&gpio 22 GPIO_ACTIVE_LOW>;
+		reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
+		clocks = <&ad7768_mclk>;
+		clock-names = "mclk";
+	};

MAINTAINERS

@@ -868,6 +868,7 @@ L:	linux-iio@vger.kernel.org
 W:	http://ez.analog.com/community/linux-device-drivers
 S:	Supported
 F:	drivers/iio/adc/ad7768-1.c
+F:	Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.txt
 
 ANALOG DEVICES INC AD9389B DRIVER
 M:	Hans Verkuil <hans.verkuil@cisco.com>