dt-bindings: pinctrl: intel: Add for new SoC

Add dt bindings document for pinmux & GPIO controller driver of
Intel Lightning Mountain SoC.
Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Link: https://lore.kernel.org/r/b59afc497e41404fea06aa48d633cba183ee944d.1573797249.git.rahul.tanwar@linux.intel.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/intel,lgm-pinctrl.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bindings/pinctrl/intel,lgm-pinctrl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Intel Lightning Mountain SoC pinmux & GPIO controller binding
+
+maintainers:
+  - Rahul Tanwar <rahul.tanwar@linux.intel.com>
+
+description: |
+  Pinmux & GPIO controller controls pin multiplexing & configuration including
+  GPIO function selection & GPIO attributes configuration.
+
+  Please refer to [1] for details of the common pinctrl bindings used by the
+  client devices.
+
+  [1] Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
+
+properties:
+  compatible:
+    const: intel,lgm-io
+
+  reg:
+    maxItems: 1
+
+# Client device subnode's properties
+patternProperties:
+  '-pins$':
+    type: object
+    description:
+      Pinctrl node's client devices use subnodes for desired pin configuration.
+      Client device subnodes use below standard properties.
+
+    properties:
+      function:
+        $ref: /schemas/types.yaml#/definitions/string
+        description:
+          A string containing the name of the function to mux to the group.
+
+      groups:
+        $ref: /schemas/types.yaml#/definitions/string-array
+        description:
+          An array of strings identifying the list of groups.
+
+      pins:
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        description:
+          List of pins to select with this function.
+
+      pinmux:
+        description: The applicable mux group.
+        allOf:
+          - $ref: "/schemas/types.yaml#/definitions/uint32-array"
+
+      bias-pull-up:
+        type: boolean
+
+      bias-pull-down:
+        type: boolean
+
+      drive-strength:
+        description: |
+          Selects the drive strength for the specified pins in mA.
+          0: 2 mA
+          1: 4 mA
+          2: 8 mA
+          3: 12 mA
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+          - enum: [0, 1, 2, 3]
+
+      slew-rate:
+        type: boolean
+        description: |
+          Sets slew rate for specified pins.
+          0: slow slew
+          1: fast slew
+
+      drive-open-drain:
+        type: boolean
+
+      output-enable:
+        type: boolean
+
+    required:
+      - function
+      - groups
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  # Pinmux controller node
+  - |
+    pinctrl: pinctrl@e2880000 {
+        compatible = "intel,lgm-pinctrl";
+        reg = <0xe2880000 0x100000>;
+
+        uart0-pins {
+             pins = <64>, /* UART_RX0 */
+                    <65>; /* UART_TX0 */
+             function = "CONSOLE_UART0";
+             pinmux = <1>,
+                      <1>;
+             groups = "CONSOLE_UART0";
+          };
+    };
+
+...