dt-bindings: pinctrl: imx8ulp: Add pinctrl binding

Add pinctrl binding doc for i.MX8ULP
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20210607061041.2654568-1-ping.bai@nxp.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/fsl,imx8ulp-pinctrl.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pinctrl/fsl,imx8ulp-pinctrl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale IMX8ULP IOMUX Controller
+
+maintainers:
+  - Jacky Bai <ping.bai@nxp.com>
+
+description:
+  Please refer to fsl,imx-pinctrl.txt and pinctrl-bindings.txt in this directory
+  for common binding part and usage.
+
+properties:
+  compatible:
+    const: fsl,imx8ulp-iomuxc1
+
+  reg:
+    maxItems: 1
+
+# Client device subnode's properties
+patternProperties:
+  'grp$':
+    type: object
+    description:
+      Pinctrl node's client devices use subnodes for desired pin configuration.
+      Client device subnodes use below standard properties.
+
+    properties:
+      fsl,pins:
+        description:
+          each entry consists of 5 integers and represents the mux and config
+          setting for one pin. The first 4 integers <mux_config_reg input_reg
+          mux_mode input_val> are specified using a PIN_FUNC_ID macro, which can
+          be found in <arch/arm64/boot/dts/freescale/imx8ulp-pinfunc.h>. The last
+          integer CONFIG is the pad setting value like pull-up on this pin. Please
+          refer to i.MX8ULP Reference Manual for detailed CONFIG settings.
+        $ref: /schemas/types.yaml#/definitions/uint32-matrix
+        items:
+          items:
+            - description: |
+                "mux_config_reg" indicates the offset of mux register.
+            - description: |
+                "input_reg" indicates the offset of select input register.
+            - description: |
+                "mux_mode" indicates the mux value to be applied.
+            - description: |
+                "input_val" indicates the select input value to be applied.
+            - description: |
+                "pad_setting" indicates the pad configuration value to be applied.
+
+    required:
+      - fsl,pins
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  # Pinmux controller node
+  - |
+    iomuxc: pinctrl@298c0000 {
+        compatible = "fsl,imx8ulp-iomuxc1";
+        reg = <0x298c0000 0x10000>;
+
+        pinctrl_lpuart5: lpuart5grp {
+            fsl,pins =
+                <0x0138 0x08F0 0x4 0x3	0x3>,
+                <0x013C 0x08EC 0x4 0x3	0x3>;
+        };
+    };
+
+...