[PATCH 4/5] dt-bindings: i2c: Add RTL9300 I2C multiplexer

[Chris Packham <chris.packham@alliedtelesis.co.nz>]

An extension of the RTL9300 SoC is to support multiplexing by selecting
the SDA pins that are being used dynamically. Add a binding that allows
us to describe hardware that makes use of this.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
 .../bindings/i2c/realtek,rtl9300-i2c-mux.yaml | 82 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 83 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c-mux.yaml

diff --git a/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c-mux.yaml b/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c-mux.yaml
new file mode 100644
index 000000000000..a64879d0fda7
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c-mux.yaml
@@ -0,0 +1,82 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/i2c/realtek,rtl9300-i2c-mux.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek RTL I2C Multiplexer
+
+maintainers:
+  - Chris Packham <chris.packham@alliedtelesis.co.nz>
+
+description: |
+  The I2C controllers on the RTL9300 support a level of multiplexing. In the
+  simple case the rtl9300-i2c binding can provide a single SDA pin per
+  controller. This binding allows a more than one SDA line to be used per
+  controller providing a level of multiplexing.
+
+properties:
+  compatible:
+    const: realtek,rtl9300-i2c-mux
+
+  i2c-parent:
+    description: phandle of the I2C bus controller that this multiplexer
+      operates on.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+allOf:
+  - $ref: i2c-mux.yaml
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - i2c-parent
+
+examples:
+  - |
+    switch@1b000000 {
+      compatible = "realtek,rtl9302c-switch", "syscon", "simple-mfd";
+      reg = <0x1b000000 0x10000>;
+
+      i2c0: i2c@36c {
+        compatible = "realtek,rtl9300-i2c";
+        realtek,control-offset = <0x36c>;
+        realtek,global-control-offset = <0x384>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+      };
+    };
+
+    base {
+      i2c-mux {
+        compatible = "realtek,rtl9300-i2c-mux";
+        #address-cells = <1>;
+        #size-cells = <0>;
+        i2c-parent = <&i2c0>;
+
+        i2c@0 {
+          reg = <0>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+          gpio@20 {
+              compatible = "nxp,pca9555";
+              gpio-controller;
+              #gpio-cells = <2>;
+              reg = <0x20>;
+          };
+        };
+
+        i2c@2 {
+          reg = <2>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+          gpio@20 {
+              compatible = "nxp,pca9555";
+              gpio-controller;
+              #gpio-cells = <2>;
+              reg = <0x20>;
+          };
+        };
+      };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 9e123e9839a5..178ac8a7e843 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19891,6 +19891,7 @@ RTL9300 I2C DRIVER (rtl9300-i2c)
 M:	Chris Packham <chris.packham@alliedtelesis.co.nz>
 L:	linux-i2c@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c-mux.yaml
 F:	Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
 F:	drivers/i2c/busses/i2c-rtl9300.c
 
-- 
2.46.1