media: dt-bindings: gpio-ir-tx: add support for GPIO IR Transmitter

Document the device tree bindings for the GPIO IR Bit Banging
Transmitter.
Signed-off-by: Sean Young <sean@mess.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/leds/irled/gpio-ir-tx.txt

+Device tree bindings for IR LED connected through gpio pin which is used as
+remote controller transmitter.
+
+Required properties:
+	- compatible: should be "gpio-ir-tx".
+	- gpios :  Should specify the IR LED GPIO, see "gpios property" in
+	  Documentation/devicetree/bindings/gpio/gpio.txt.  Active low LEDs
+	  should be indicated using flags in the GPIO specifier.
+
+Example:
+	irled@0 {
+		compatible = "gpio-ir-tx";
+		gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
+	};