dt-bindings: clock: mediatek: Add new bindings of MediaTek frequency hopping

Add the new binding documentation for MediaTek frequency hopping
and spread spectrum clocking control.

Co-developed-by: Edward-JW Yang <[e-mail]>
Signed-off-by: Edward-JW Yang <[e-mail]>
Signed-off-by: Johnson Wang <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Chen-Yu Tsai <[e-mail]>

Documentation/devicetree/bindings/clock/mediatek,mt8186-fhctl.yaml

···
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/mediatek,mt8186-fhctl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek frequency hopping and spread spectrum clocking control
+
+maintainers:
+  - Edward-JW Yang <[e-mail]>
+
+description: |
+  Frequency hopping control (FHCTL) is a piece of hardware that control
+  some PLLs to adopt "hopping" mechanism to adjust their frequency.
+  Spread spectrum clocking (SSC) is another function provided by this hardware.
+
+properties:
+  compatible:
+    const: mediatek,mt8186-fhctl
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    description: Phandles of the PLL with FHCTL hardware capability.
+    minItems: 1
+    maxItems: 30
+
+  mediatek,hopping-ssc-percent:
+    description: The percentage of spread spectrum clocking for one PLL.
+    minItems: 1
+    maxItems: 30
+    items:
+      default: 0
+      minimum: 0
+      maximum: 8
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/mt8186-clk.h>
+    fhctl: fhctl@1000ce00 {
+        compatible = "mediatek,mt8186-fhctl";
+        reg = <0x1000ce00 0x200>;
+        clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
+        mediatek,hopping-ssc-percent = <3>;
+    };