dt-bindings: pinctrl: Add bindings for pinctrl-microchip-sgpio driver

This adds DT bindings for the Microsemi/Microchip SGPIO controller,
bindings microchip,sparx5-sgpio, mscc,ocelot-sgpio and
mscc,luton-sgpio.
Signed-off-by: NLars Povlsen <lars.povlsen@microchip.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201113145151.68900-2-lars.povlsen@microchip.comSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/microchip,sparx5-sgpio.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pinctrl/microchip,sparx5-sgpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microsemi/Microchip Serial GPIO controller
+
+maintainers:
+  - Lars Povlsen <lars.povlsen@microchip.com>
+
+description: |
+  By using a serial interface, the SIO controller significantly extend
+  the number of available GPIOs with a minimum number of additional
+  pins on the device. The primary purpose of the SIO controllers is to
+  connect control signals from SFP modules and to act as an LED
+  controller.
+
+properties:
+  $nodename:
+    pattern: "^gpio@[0-9a-f]+$"
+
+  compatible:
+    enum:
+      - microchip,sparx5-sgpio
+      - mscc,ocelot-sgpio
+      - mscc,luton-sgpio
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  microchip,sgpio-port-ranges:
+    description: This is a sequence of tuples, defining intervals of
+      enabled ports in the serial input stream. The enabled ports must
+      match the hardware configuration in order for signals to be
+      properly written/read to/from the controller holding
+      registers. Being tuples, then number of arguments must be
+      even. The tuples mast be ordered (low, high) and are
+      inclusive.
+    $ref: /schemas/types.yaml#/definitions/uint32-matrix
+    items:
+      items:
+        - description: |
+            "low" indicates start bit number of range
+          minimum: 0
+          maximum: 31
+        - description: |
+            "high" indicates end bit number of range
+          minimum: 0
+          maximum: 31
+    minItems: 1
+    maxItems: 32
+
+  bus-frequency:
+    description: The sgpio controller frequency (Hz). This dictates
+      the serial bitstream speed, which again affects the latency in
+      getting control signals back and forth between external shift
+      registers. The speed must be no larger than half the system
+      clock, and larger than zero.
+    default: 12500000
+
+patternProperties:
+  "^gpio@[0-1]$":
+    type: object
+    properties:
+      compatible:
+        const: microchip,sparx5-sgpio-bank
+
+      reg:
+        description: |
+          The GPIO bank number. "0" is designates the input pin bank,
+          "1" the output bank.
+        maxItems: 1
+
+      gpio-controller: true
+
+      '#gpio-cells':
+        description: |
+         Specifies the pin (port and bit) and flags. Note that the
+         SGIO pin is defined by *2* numbers, a port number between 0
+         and 31, and a bit index, 0 to 3. The maximum bit number is
+         controlled indirectly by the "ngpios" property: (ngpios/32).
+        const: 3
+
+      ngpios:
+        description: The numbers of GPIO's exposed. This must be a
+          multiple of 32.
+        minimum: 32
+        maximum: 128
+
+    required:
+      - compatible
+      - reg
+      - gpio-controller
+      - '#gpio-cells'
+      - ngpios
+
+    additionalProperties: false
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - microchip,sgpio-port-ranges
+  - "#address-cells"
+  - "#size-cells"
+
+examples:
+  - |
+    sgpio2: gpio@1101059c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+      compatible = "microchip,sparx5-sgpio";
+      clocks = <&sys_clk>;
+      pinctrl-0 = <&sgpio2_pins>;
+      pinctrl-names = "default";
+      reg = <0x1101059c 0x100>;
+      microchip,sgpio-port-ranges = <0 0>, <16 18>, <28 31>;
+      bus-frequency = <25000000>;
+      sgpio_in2: gpio@0 {
+        reg = <0>;
+        compatible = "microchip,sparx5-sgpio-bank";
+        gpio-controller;
+        #gpio-cells = <3>;
+        ngpios = <96>;
+      };
+      sgpio_out2: gpio@1 {
+        compatible = "microchip,sparx5-sgpio-bank";
+        reg = <1>;
+        gpio-controller;
+        #gpio-cells = <3>;
+        ngpios = <96>;
+      };
+    };