dt-bindings: gpio: add common consumer GPIO lines

Typical GPIO lines like enable, powerdown, reset or wakeup are not
documented as common, which leads to new variations of these (e.g.
pwdn-gpios).  Add a common schema which serves also as a documentation
for preferred naming.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Documentation/devicetree/bindings/gpio/gpio-consumer-common.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-consumer-common.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common GPIO lines
+
+maintainers:
+  - Bartosz Golaszewski <brgl@bgdev.pl>
+  - Linus Walleij <linus.walleij@linaro.org>
+
+description:
+  Pay attention to using proper GPIO flag (e.g. GPIO_ACTIVE_LOW) for the GPIOs
+  using inverted signal (e.g. RESETN).
+
+select: true
+
+properties:
+  enable-gpios:
+    maxItems: 1
+    description:
+      GPIO connected to the enable control pin.
+
+  reset-gpios:
+    description:
+      GPIO (or GPIOs for power sequence) connected to the device reset pin
+      (e.g. RESET or RESETN).
+
+  powerdown-gpios:
+    maxItems: 1
+    description:
+      GPIO connected to the power down pin (hardware power down or power cut,
+      e.g. PD or PWDN).
+
+  pwdn-gpios:
+    maxItems: 1
+    description: Use powerdown-gpios
+    deprecated: true
+
+  wakeup-gpios:
+    maxItems: 1
+    description:
+      GPIO connected to the pin waking up the device from suspend or other
+      power-saving modes.
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - mmc-pwrseq-simple
+    then:
+      properties:
+        reset-gpios:
+          minItems: 1
+          maxItems: 32
+    else:
+      properties:
+        reset-gpios:
+          maxItems: 1
+
+additionalProperties: true