dt-bindings: mfd: Add Broadcom's MISC block

Broadcom's MISC is an MFD hardware block used on some of their SoCs like
bcm63xx and bcm4908. At this point only PCIe reset is fully understood
and documented. More functions may be added later.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/brcm,misc.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/brcm,misc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom's MISC block
+
+maintainers:
+  - Rafał Miłecki <rafal@milecki.pl>
+
+description: |
+  Broadcom's MISC is a hardware block used on some SoCs (e.g. bcm63xx and
+  bcm4908). It's used to implement some simple functions like a watchdog, PCIe
+  reset, UniMAC control and more.
+
+properties:
+  compatible:
+    items:
+      - const: brcm,misc
+      - const: simple-mfd
+
+  reg:
+    description: MISC block registers
+
+  ranges: true
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+patternProperties:
+  '^reset-controller@[a-f0-9]+$':
+    $ref: ../reset/brcm,bcm4908-misc-pcie-reset.yaml
+
+additionalProperties: false
+
+required:
+  - reg
+  - '#address-cells'
+  - '#size-cells'
+
+examples:
+  - |
+    misc@ff802600 {
+        compatible = "brcm,misc", "simple-mfd";
+        reg = <0xff802600 0xe4>;
+
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges = <0x0 0x0 0xe4>;
+
+        reset-controller@44 {
+            compatible = "brcm,bcm4908-misc-pcie-reset";
+            reg = <0x44 0x4>;
+            #reset-cells = <1>;
+        };
+    };