dt-bindings: spmi: document binding for the Mediatek SPMI controller

This adds documentation for the SPMI controller found on Mediatek SoCs.

Link: https://lore.kernel.org/r/20211119034613.32489-3-james.lo@mediatek.comReviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: James Lo <james.lo@mediatek.com>
Signed-off-by: Hsin-Hsiung Wang <hsin-hsiung.wang@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20211216190812.1574801-4-sboyd@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/spmi/mtk,spmi-mtk-pmif.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spmi/mtk,spmi-mtk-pmif.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Mediatek SPMI Controller Device Tree Bindings
+
+maintainers:
+  - Hsin-Hsiung Wang <hsin-hsiung.wang@mediatek.com>
+
+description: |+
+  On MediaTek SoCs the PMIC is connected via SPMI and the controller allows
+  for multiple SoCs to control a single SPMI master.
+
+allOf:
+  - $ref: "spmi.yaml"
+
+properties:
+  compatible:
+    enum:
+      - mediatek,mt6873-spmi
+      - mediatek,mt8195-spmi
+
+  reg:
+    maxItems: 2
+
+  reg-names:
+    items:
+      - const: pmif
+      - const: spmimst
+
+  clocks:
+    minItems: 3
+    maxItems: 3
+
+  clock-names:
+    items:
+      - const: pmif_sys_ck
+      - const: pmif_tmr_ck
+      - const: spmimst_clk_mux
+
+  assigned-clocks:
+    maxItems: 1
+
+  assigned-clock-parents:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - clocks
+  - clock-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/mt8192-clk.h>
+
+    spmi: spmi@10027000 {
+        compatible = "mediatek,mt6873-spmi";
+        reg = <0x10027000 0xe00>,
+              <0x10029000 0x100>;
+        reg-names = "pmif", "spmimst";
+        clocks = <&infracfg CLK_INFRA_PMIC_AP>,
+                 <&infracfg CLK_INFRA_PMIC_TMR>,
+                 <&topckgen CLK_TOP_SPMI_MST_SEL>;
+        clock-names = "pmif_sys_ck",
+                      "pmif_tmr_ck",
+                      "spmimst_clk_mux";
+        assigned-clocks = <&topckgen CLK_TOP_PWRAP_ULPOSC_SEL>;
+        assigned-clock-parents = <&topckgen CLK_TOP_OSC_D10>;
+    };
+...