iio: humidity: add HDC100x support

Add support for the HDC100x temperature and humidity sensors
including the resistive heater element.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x b/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x
new file mode 100644
index 0000000..b72bb62
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-humidity-hdc100x
@@ -0,0 +1,9 @@
+What:		/sys/bus/iio/devices/iio:deviceX/out_current_heater_raw
+What:		/sys/bus/iio/devices/iio:deviceX/out_current_heater_raw_available
+KernelVersion:	4.3
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Controls the heater device within the humidity sensor to get
+		rid of excess condensation.
+
+		Valid control values are 0 = OFF, and 1 = ON.