staging: mt7621-gpio: dt-bindings: add documentation for mt7621-gpio

This commit add missing dt bindings documentation for mt7621-gpio
driver. There is some missing stuff here about interrupts with is
not also being used in the mt7621.dtsi file. So just include in
staging a incomplete version before moving this to kernel's dt-bindings
place.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/mt7621-gpio/mediatek,mt7621-gpio.txt b/drivers/staging/mt7621-gpio/mediatek,mt7621-gpio.txt
new file mode 100644 (file)
index 0000000..54de9f7
--- /dev/null
+++ b/drivers/staging/mt7621-gpio/mediatek,mt7621-gpio.txt
@@ -0,0 +1,51 @@
+Mediatek SoC GPIO controller bindings
+
+The IP core used inside these SoCs has 3 banks of 32 GPIOs each.
+The registers of all the banks are interwoven inside one single IO range.
+We load one GPIO controller instance per bank. To make this possible
+we support 2 types of nodes. The parent node defines the memory I/O range and
+has 3 children each describing a single bank.
+
+Required properties for the top level node:
+- compatible:
+  - "mediatek,mt7621-gpio" for Mediatek controllers
+- reg : Physical base address and length of the controller's registers
+
+Required properties for the GPIO bank node:
+- compatible:
+  - "mediatek,mt7621-gpio-bank" for Mediatek banks
+- #gpio-cells : Should be two.
+  - first cell is the pin number
+  - second cell is used to specify optional parameters (unused)
+- gpio-controller : Marks the device node as a GPIO controller
+- reg : The id of the bank that the node describes.
+
+Example:
+       gpio@600 {
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               compatible = "mediatek,mt7621-gpio";
+               reg = <0x600 0x100>;
+
+               gpio0: bank@0 {
+                       reg = <0>;
+                       compatible = "mediatek,mt7621-gpio-bank";
+                       gpio-controller;
+                       #gpio-cells = <2>;
+               };
+
+               gpio1: bank@1 {
+                       reg = <1>;
+                       compatible = "mediatek,mt7621-gpio-bank";
+                       gpio-controller;
+                       #gpio-cells = <2>;
+               };
+
+               gpio2: bank@2 {
+                       reg = <2>;
+                       compatible = "mediatek,mt7621-gpio-bank";
+                       gpio-controller;
+                       #gpio-cells = <2>;
+               };
+       };