dt-bindings: iio: afe: add binding for current-sense-amplifier

Similar to current sense shunts, but an amplifier enables the use
of a smaller sense resistance.
Signed-off-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.txt

+Current Sense Amplifier
+=======================
+
+When an io-channel measures the output voltage from a current sense
+amplifier, the interesting mesaurement is almost always the current
+through the sense resistor, not the voltage output. This binding
+describes such a current sense circuit.
+
+Required properties:
+- compatible : "current-sense-amplifier"
+- io-channels : Channel node of a voltage io-channel.
+- sense-resistor-micro-ohms : The sense resistance in microohms.
+
+Optional properties:
+- sense-gain-mult: Amplifier gain multiplier. The default is <1>.
+- sense-gain-div: Amplifier gain divider. The default is <1>.
+
+Example:
+
+sysi {
+	compatible = "current-sense-amplifier";
+	io-channels = <&tiadc 0>;
+
+	sense-resistor-micro-ohms = <20000>;
+	sense-gain-mul = <50>;
+};

MAINTAINERS

@@ -6902,6 +6902,7 @@ IIO UNIT CONVERTER
 M:	Peter Rosin <peda@axentia.se>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.txt
 F:	Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
 F:	Documentation/devicetree/bindings/iio/afe/voltage-divider.txt