dt-bindings: add BCM6358 pincontroller binding documentation

Add binding documentation for the pincontrol core found in BCM6358 SoCs.
Co-developed-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210324081923.20379-9-noltari@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/brcm,bcm6358-pinctrl.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pinctrl/brcm,bcm6358-pinctrl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM6358 pin controller
+
+maintainers:
+  - Álvaro Fernández Rojas <noltari@gmail.com>
+  - Jonas Gorski <jonas.gorski@gmail.com>
+
+description:
+  Bindings for Broadcom's BCM6358 memory-mapped pin controller.
+
+properties:
+  compatible:
+    const: brcm,bcm6358-pinctrl
+
+  reg:
+    maxItems: 1
+
+patternProperties:
+  '-pins$':
+    type: object
+    $ref: pinmux-node.yaml#
+
+    properties:
+      function:
+        enum: [ ebi_cs, uart1, serial_led, legacy_led, led, spi_cs, utopia,
+                pwm_syn_clk, sys_irq ]
+
+      pins:
+        enum: [ ebi_cs_grp, uart1_grp, serial_led_grp, legacy_led_grp,
+                led_grp, spi_cs_grp, utopia_grp, pwm_syn_clk, sys_irq_grp ]
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    pinctrl@18 {
+      compatible = "brcm,bcm6358-pinctrl";
+      reg = <0x18 0x4>;
+
+      pinctrl_ebi_cs: ebi_cs-pins {
+        function = "ebi_cs";
+        groups = "ebi_cs_grp";
+      };
+
+      pinctrl_uart1: uart1-pins {
+        function = "uart1";
+        groups = "uart1_grp";
+      };
+
+      pinctrl_serial_led: serial_led-pins {
+        function = "serial_led";
+        groups = "serial_led_grp";
+      };
+
+      pinctrl_legacy_led: legacy_led-pins {
+        function = "legacy_led";
+        groups = "legacy_led_grp";
+      };
+
+      pinctrl_led: led-pins {
+        function = "led";
+        groups = "led_grp";
+      };
+
+      pinctrl_spi_cs_23: spi_cs-pins {
+        function = "spi_cs";
+        groups = "spi_cs_grp";
+      };
+
+      pinctrl_utopia: utopia-pins {
+        function = "utopia";
+        groups = "utopia_grp";
+      };
+
+      pinctrl_pwm_syn_clk: pwm_syn_clk-pins {
+        function = "pwm_syn_clk";
+        groups = "pwm_syn_clk_grp";
+      };
+
+      pinctrl_sys_irq: sys_irq-pins {
+        function = "sys_irq";
+        groups = "sys_irq_grp";
+      };
+    };