dt-bindings: mfd: Add Broadcom CRU

CRU is a block used in e.g. Northstar devices. It can be seen in the
bcm5301x.dtsi and this binding documents its proper usage.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

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

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/brcm,cru.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom CRU
+
+maintainers:
+  - Rafał Miłecki <rafal@milecki.pl>
+
+description: |
+  Broadcom CRU ("Clock and Reset Unit" or "Central Resource Unit") is a hardware
+  block grouping smaller blocks. On Broadcom Northstar platform it contains e.g.
+  clocks, pinctrl, USB PHY and thermal.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - brcm,ns-cru
+      - const: simple-mfd
+
+  reg:
+    description: CRU registers
+
+  ranges: true
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  pinctrl:
+    $ref: ../pinctrl/brcm,ns-pinmux.yaml
+
+patternProperties:
+  '^clock-controller@[a-f0-9]+$':
+    $ref: ../clock/brcm,iproc-clocks.yaml
+
+  '^thermal@[a-f0-9]+$':
+    $ref: ../thermal/brcm,ns-thermal.yaml
+
+additionalProperties: false
+
+required:
+  - reg
+
+examples:
+  - |
+    cru-bus@1800c100 {
+        compatible = "brcm,ns-cru", "simple-mfd";
+        reg = <0x1800c100 0x1d0>;
+        ranges;
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        clock-controller@100 {
+            #clock-cells = <1>;
+            compatible = "brcm,nsp-lcpll0";
+            reg = <0x100 0x14>;
+            clocks = <&osc>;
+            clock-output-names = "lcpll0", "pcie_phy", "sdio", "ddr_phy";
+        };
+
+        clock-controller@140 {
+            #clock-cells = <1>;
+            compatible = "brcm,nsp-genpll";
+            reg = <0x140 0x24>;
+            clocks = <&osc>;
+            clock-output-names = "genpll", "phy", "ethernetclk", "usbclk",
+                                 "iprocfast", "sata1", "sata2";
+        };
+
+        pinctrl {
+            compatible = "brcm,bcm4708-pinmux";
+            offset = <0x1c0>;
+        };
+
+        thermal@2c0 {
+            compatible = "brcm,ns-thermal";
+            reg = <0x2c0 0x10>;
+            #thermal-sensor-cells = <0>;
+        };
+    };