[v6 1/2] dt-bindings: gpio: aspeed: Add SGPIO support

[Hongwei Zhang <hongweiz@ami.com>]

Add bindings to support SGPIO on AST2400 or AST2500.

Signed-off-by: Hongwei Zhang <hongweiz@ami.com>
---
 .../devicetree/bindings/gpio/sgpio-aspeed.txt      | 55 ++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/sgpio-aspeed.txt

diff --git a/Documentation/devicetree/bindings/gpio/sgpio-aspeed.txt b/Documentation/devicetree/bindings/gpio/sgpio-aspeed.txt
new file mode 100644
index 0000000..f9ed438
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/sgpio-aspeed.txt
@@ -0,0 +1,55 @@
+Aspeed SGPIO controller Device Tree Bindings
+-------------------------------------------
+
+This SGPIO controller is for ASPEED AST2500 SoC, it supports up to 80 full 
+featured Serial GPIOs. Each of the Serial GPIO pins can be programmed to 
+support the following options:
+- Support interrupt option for each input port and various interrupt 
+  sensitivity option (level-high, level-low, edge-high, edge-low)
+- Support reset tolerance option for each output port
+- Directly connected to APB bus and its shift clock is from APB bus clock
+  divided by a programmable value.
+- Co-work with external signal-chained TTL components (74LV165/74LV595)
+
+
+Required properties:
+
+- compatible		: Either "aspeed,ast2400-sgpio" or "aspeed,ast2500-sgpio"
+
+- #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
+
+- ngpios		: number of GPIO pins to serialise. 
+			  (should be multiple of 8, up to 80 pins)
+
+- clocks                : A phandle to the APB clock for SGPM clock division
+
+- bus-frequency		: SGPM CLK frequency
+
+
+The sgpio and interrupt properties are further described in their respective bindings documentation:
+
+- Documentation/devicetree/bindings/sgpio/gpio.txt
+- Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+
+  Example:
+	sgpio: sgpio@1e780200 {
+		#gpio-cells = <2>;
+		compatible = "aspeed,ast2500-sgpio";
+		gpio-controller;
+		interrupts = <40>;
+		reg = <0x1e780200 0x0100>;
+		clocks = <&syscon ASPEED_CLK_APB>;
+		interrupt-controller;
+		ngpios = <8>;
+		bus-frequency = <12000000>;
+	};
-- 
2.7.4