dt-bindings: gpio: Convert X-Powers AXP209 GPIO binding to a schema

The X-Powers AXP PMICs feature a GPIO Controller supported by Linux
thanks to its device tree binding.

Now that we have the DT validation in place, let's convert the device
tree bindings for that driver over to a YAML schema.

Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-gpio@vger.kernel.org
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210924071614.868307-1-maxime@cerno.tech

Documentation/devicetree/bindings/gpio/gpio-axp209.txt

-AXP209 GPIO & pinctrl controller
-
-This driver follows the usual GPIO bindings found in
-Documentation/devicetree/bindings/gpio/gpio.txt
-
-This driver follows the usual pinctrl bindings found in
-Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
-
-This driver employs the per-pin muxing pattern.
-
-Required properties:
-- compatible: Should be one of:
-	- "x-powers,axp209-gpio"
-	- "x-powers,axp813-gpio"
-- #gpio-cells: Should be two. The first cell is the pin number and the
-  second is the GPIO flags.
-- gpio-controller: Marks the device node as a GPIO controller.
-
-This node must be a subnode of the axp20x PMIC, documented in
-Documentation/devicetree/bindings/mfd/axp20x.txt
-
-Example:
-
-axp209: pmic@34 {
-	compatible = "x-powers,axp209";
-	reg = <0x34>;
-	interrupt-parent = <&nmi_intc>;
-	interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
-	interrupt-controller;
-	#interrupt-cells = <1>;
-
-	axp_gpio: gpio {
-		compatible = "x-powers,axp209-gpio";
-		gpio-controller;
-		#gpio-cells = <2>;
-	};
-};
-
-The GPIOs can be muxed to other functions and therefore, must be a subnode of
-axp_gpio.
-
-Example:
-
-&axp_gpio {
-	gpio0_adc: gpio0-adc {
-		pins = "GPIO0";
-		function = "adc";
-	};
-};
-
-&example_node {
-	pinctrl-names = "default";
-	pinctrl-0 = <&gpio0_adc>;
-};
-
-GPIOs and their functions
--------------------------
-
-Each GPIO is independent from the other (i.e. GPIO0 in gpio_in function does
-not force GPIO1 and GPIO2 to be in gpio_in function as well).
-
-axp209
-------
-GPIO	|	Functions
-------------------------
-GPIO0	|	gpio_in, gpio_out, ldo, adc
-GPIO1	|	gpio_in, gpio_out, ldo, adc
-GPIO2	|	gpio_in, gpio_out
-
-axp813
-------
-GPIO	|	Functions
-------------------------
-GPIO0	|	gpio_in, gpio_out, ldo, adc
-GPIO1	|	gpio_in, gpio_out, ldo

Documentation/devicetree/bindings/gpio/x-powers,axp209-gpio.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/gpio/x-powers,axp209-gpio.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: X-Powers AXP209 GPIO Device Tree Bindings
+
+maintainers:
+  - Chen-Yu Tsai <wens@csie.org>
+
+properties:
+  "#gpio-cells":
+    const: 2
+    description: >
+      The first cell is the pin number and the second is the GPIO flags.
+
+  compatible:
+    oneOf:
+      - enum:
+          - x-powers,axp209-gpio
+          - x-powers,axp813-gpio
+      - items:
+          - const: x-powers,axp803-gpio
+          - const: x-powers,axp813-gpio
+
+  gpio-controller: true
+
+patternProperties:
+  "^.*-pins?$":
+    $ref: /schemas/pinctrl/pinmux-node.yaml#
+
+    properties:
+      pins:
+        items:
+          enum:
+            - GPIO0
+            - GPIO1
+            - GPIO2
+
+      function:
+        enum:
+          - adc
+          - ldo
+          - gpio_in
+          - gpio_out
+
+required:
+  - compatible
+  - "#gpio-cells"
+  - gpio-controller
+
+additionalProperties: false
+
+...