[PATCH v5 2/5] dt-bindings: gpio: add raspberry pi GPIO expander binding

[Baruch Siach]

The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware over
I2C. The firmware mailbox interface allows the ARM core to control the
GPIO lines.

Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
v5:
  * Remove the 'firmware' property
  * Note that the gpio node is a child of the firmware node

v4:
  * Move the example gpio node under the firmware node
  * Rename gpio node name to plain 'gpio'

v3:
  * Rename node name.

v2:
  * Rename compatible string to raspberrypi,firmware-gpio
---
 .../bindings/gpio/raspberrypi,firmware-gpio.txt    | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/raspberrypi,firmware-gpio.txt

diff --git a/Documentation/devicetree/bindings/gpio/raspberrypi,firmware-gpio.txt b/Documentation/devicetree/bindings/gpio/raspberrypi,firmware-gpio.txt
new file mode 100644
index 000000000000..ce97265e23ba
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/raspberrypi,firmware-gpio.txt
@@ -0,0 +1,30 @@
+Raspberry Pi GPIO expander
+
+The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The
+firmware exposes a mailbox interface that allows the ARM core to control the
+GPIO lines on the expander.
+
+The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi
+firmware node.
+
+Required properties:
+
+- compatible : Should be "raspberrypi,firmware-gpio"
+- gpio-controller : Marks the device node as a gpio controller
+- #gpio-cells : Should be two.  The first cell is the pin number, and
+  the second cell is used to specify the gpio polarity:
+  0 = active high
+  1 = active low
+
+Example:
+
+firmware: firmware-rpi {
+	compatible = "raspberrypi,bcm2835-firmware";
+	mboxes = <&mailbox>;
+
+	expgpio: gpio {
+		 compatible = "raspberrypi,firmware-gpio";
+		 gpio-controller;
+		 #gpio-cells = <2>;
+	 };
+};
-- 
2.16.1