HID: i2c-hid: add DT bindings

Add device tree based support for HID over I2C devices.

Tested on an Odroid-X board with a Synaptics touchpad.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/include/linux/i2c/i2c-hid.h b/include/linux/i2c/i2c-hid.h
index 60e411d..7aa901d 100644
--- a/include/linux/i2c/i2c-hid.h
+++ b/include/linux/i2c/i2c-hid.h
@@ -19,7 +19,8 @@
  * @hid_descriptor_address: i2c register where the HID descriptor is stored.
  *
  * Note that it is the responsibility of the platform driver (or the acpi 5.0
- * driver) to setup the irq related to the gpio in the struct i2c_board_info.
+ * driver, or the flattened device tree) to setup the irq related to the gpio in
+ * the struct i2c_board_info.
  * The platform driver should also setup the gpio according to the device:
  *
  * A typical example is the following: