gpio: dt-bindings: Add documentation for Aspeed GPIO controllers

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Acked-by: Joel Stanley <joel@jms.id.au>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt b/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt
new file mode 100644 (file)
index 0000000..393bb2e
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-aspeed.txt
@@ -0,0 +1,36 @@
+Aspeed GPIO controller Device Tree Bindings
+-------------------------------------------
+
+Required properties:
+- compatible           : Either "aspeed,ast2400-gpio" or "aspeed,ast2500-gpio"
+
+- #gpio-cells          : Should be two
+                         - First cell is the GPIO line number
+                         - Second cell is used to specify optional
+                           parameters (unused)
+
+- reg                  : Address and length of the register set for the device
+- gpio-controller      : Marks the device node as a GPIO controller.
+- interrupts           : Interrupt specifier (see interrupt bindings for
+                         details)
+- interrupt-controller : Mark the GPIO controller as an interrupt-controller
+
+Optional properties:
+
+- interrupt-parent     : The parent interrupt controller, optional if inherited
+
+The gpio and interrupt properties are further described in their respective
+bindings documentation:
+
+- Documentation/devicetree/bindings/gpio/gpio.txt
+- Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+
+  Example:
+       gpio@1e780000 {
+               #gpio-cells = <2>;
+               compatible = "aspeed,ast2400-gpio";
+               gpio-controller;
+               interrupts = <20>;
+               reg = <0x1e780000 0x1000>;
+               interrupt-controller;
+       };