[PATCH V4 2/3] dt-bindings: gpio: zynqmp: Add binding documentation for modepin

[Piyush Mehta <piyush.mehta@xilinx.com>]

This patch adds DT binding document for zynqmp modepin GPIO controller.
Modepin GPIO controller has four GPIO pins which can be configurable
as input or output.

Modepin driver is a bridge between the peripheral driver and GPIO pins.
It has set and get APIs for accessing GPIO pins, based on the device-tree
entry of reset-gpio property in the peripheral driver, every pin can be
configured as input/output and trigger GPIO pin.

For more information please refer zynqMp TRM link:
Link: https://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrascale-trm.pdf
Chapter 2: Signals, Interfaces, and Pins
Table 2-2: Clock, Reset, and Configuration Pins - PS_MODE

Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
Changes in v2:
- Addressed review comments: Update commit message

Review Comments:
https://lore.kernel.org/linux-arm-kernel/20210615080553.2021061-2-piyush.mehta@xilinx.com/T/#mbd1fbda813e33b19397b350bde75747c92a0d7e1
https://lore.kernel.org/linux-arm-kernel/20210615080553.2021061-2-piyush.mehta@xilinx.com/T/#me82b1444ab3776162cdb0077dfc9256365c7e736

Changes in v3:
- Addressed Rob and Michal review comments:
  - Update DT example. 

Review Comments:
https://lore.kernel.org/linux-arm-kernel/YRbBnRS0VosXcZWz@robh.at.kernel.org/
https://lore.kernel.org/linux-arm-kernel/d71ad7f9-6972-8cc0-6dfb-b5306c9900d0@xilinx.com/
---
 .../bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml    | 41 ++++++++++++++++++++++
 .../bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml    | 43 ++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml

diff --git a/Documentation/devicetree/bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml b/Documentation/devicetree/bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml
new file mode 100644
index 0000000..31c0fc3
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/xlnx,zynqmp-gpio-modepin.yaml
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/gpio/xlnx,zynqmp-gpio-modepin.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: ZynqMP Mode Pin GPIO controller
+
+description:
+  PS_MODE is 4-bits boot mode pins sampled on POR deassertion. Mode Pin
+  GPIO controller with configurable from numbers of pins (from 0 to 3 per
+  PS_MODE). Every pin can be configured as input/output.
+
+maintainers:
+  - Piyush Mehta <piyush.mehta@xilinx.com>
+
+properties:
+  compatible:
+    const: xlnx,zynqmp-gpio-modepin
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+
+required:
+  - compatible
+  - gpio-controller
+  - "#gpio-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    zynqmp-firmware {
+        gpio {
+            compatible = "xlnx,zynqmp-gpio-modepin";
+            gpio-controller;
+            #gpio-cells = <2>;
+        };
+    };
+
+...
-- 
2.7.4