dt-bindings: iio: adc: Add common ADCs properties to a separate file

There are several ADC drivers that depend on the same device tree
bindings. Rather than continue to duplicate the properties, this patch
adds a common adc binding document that can be referenced. For beginning,
only two properties are documented.

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>

diff --git a/Documentation/devicetree/bindings/iio/adc/adc.txt b/Documentation/devicetree/bindings/iio/adc/adc.txt
new file mode 100644 (file)
index 0000000..5bbaa33
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adc.txt
@@ -0,0 +1,23 @@
+Common ADCs properties
+
+Optional properties for child nodes:
+- bipolar : Boolean, if set the channel is used in bipolar mode.
+- diff-channels : Differential channels muxed for this ADC. The first value
+               specifies the positive input pin, the second value the negative
+               input pin.
+
+Example:
+       adc@0 {
+               compatible = "some,adc";
+               ...
+               channel@0 {
+                       bipolar;
+                       diff-channels = <0 1>;
+                       ...
+               };
+
+               channel@1 {
+                       diff-channels = <2 3>;
+                       ...
+               };
+       };