dt-bindings: clk: rs9: Add Renesas 9-series I2C PCIe clock generator

Add binding for Renesas 9-series PCIe clock generators. This binding
is designed to support 9FGV/9DBV/9DMV/9FGL/9DML/9QXL/9SQ series I2C
PCIe clock generators, currently the only tested and supported chip
is 9FGV0241.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20220226040723.143705-1-marex@denx.deReviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/renesas,9series.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/renesas,9series.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Binding for Renesas 9-series I2C PCIe clock generators
+
+description: |
+  The Renesas 9-series are I2C PCIe clock generators providing
+  from 1 to 20 output clocks.
+
+  When referencing the provided clock in the DT using phandle
+  and clock specifier, the following mapping applies:
+
+  - 9FGV0241:
+    0 -- DIF0
+    1 -- DIF1
+
+maintainers:
+  - Marek Vasut <marex@denx.de>
+
+properties:
+  compatible:
+    enum:
+      - renesas,9fgv0241
+
+  reg:
+    description: I2C device address
+    enum: [ 0x68, 0x6a ]
+
+  '#clock-cells':
+    const: 1
+
+  clocks:
+    items:
+      - description: XTal input clock
+
+  renesas,out-amplitude-microvolt:
+    enum: [ 600000, 700000, 800000, 900000 ]
+    description: Output clock signal amplitude
+
+  renesas,out-spread-spectrum:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [ 100000, 99750, 99500 ]
+    description: Output clock down spread in pcm (1/1000 of percent)
+
+patternProperties:
+  "^DIF[0-19]$":
+    type: object
+    description:
+      Description of one of the outputs (DIF0..DIF19).
+
+    properties:
+      renesas,slew-rate:
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [ 2000000, 3000000 ]
+        description: Output clock slew rate select in V/ns
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - '#clock-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    /* 25MHz reference crystal */
+    ref25: ref25m {
+        compatible = "fixed-clock";
+        #clock-cells = <0>;
+        clock-frequency = <25000000>;
+    };
+
+    i2c@0 {
+        reg = <0x0 0x100>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        rs9: clock-generator@6a {
+            compatible = "renesas,9fgv0241";
+            reg = <0x6a>;
+            #clock-cells = <1>;
+
+            clocks = <&ref25m>;
+
+            DIF0 {
+                renesas,slew-rate = <3000000>;
+            };
+        };
+    };
+
+...