iio:magnetometer:hmc5843 - add basic dt support

Compatible string, documenation and an optional gpio
for the dataready pin.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/Documentation/devicetree/bindings/iio/magnetometer/hmc5843.txt b/Documentation/devicetree/bindings/iio/magnetometer/hmc5843.txt
new file mode 100644
index 0000000..90d5f34
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/magnetometer/hmc5843.txt
@@ -0,0 +1,17 @@
+* Honeywell HMC5843 magnetometer sensor
+
+Required properties:
+
+  - compatible : should be "honeywell,hmc5843"
+  - reg : the I2C address of the magnetometer - typically 0x1e
+
+Optional properties:
+
+  - gpios : should be device tree identifier of the magnetometer DRDY pin
+
+Example:
+
+hmc5843@1e {
+        compatible = "honeywell,hmc5843"
+        reg = <0x1e>;
+};