ARM: dts: bcm2711-rpi: Add pinctrl-based multiplexing for I2C0

BCM2711-based Raspberry Pi boards (4B, CM4 and 400) multiplex the I2C0
controller over two sets of pins, GPIO0+1 and GPIO44+45. The former is
exposed on the 40-pin header, while the latter is used for the CSI and
DSI connectors.

Add a pinctrl-based I2C bus multiplexer to bcm2711-rpi.dtsi to model
this multiplexing. The two child buses are named i2c0_0 and i2c0_1.

Note that if you modified the dts before to add devices to the i2c bus
appearing on pins gpio0 + gpio1 (either directly in the dts or using an
overlay), you have to put these into the i2c0_0 node introduced here
now.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20240402000424.4650-8-laurent.pinchart@ideasonboard.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

arch/arm/boot/dts/broadcom/bcm2711-rpi.dtsi

@@ -17,6 +17,30 @@
 		pcie0 = &pcie0;
 		blconfig = &blconfig;
 	};
+
+	i2c0mux: i2c-mux0 {
+		compatible = "i2c-mux-pinctrl";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c-parent = <&i2c0>;
+
+		pinctrl-names = "i2c0", "i2c0-vc";
+		pinctrl-0 = <&i2c0_gpio0>;
+		pinctrl-1 = <&i2c0_gpio44>;
+
+		i2c0_0: i2c@0 {
+			reg = <0>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+		};
+
+		i2c0_1: i2c@1 {
+			reg = <1>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+		};
+	};
 };
 
 &firmware {
@@ -49,6 +73,11 @@
 	clocks = <&firmware_clocks 4>;
 };
 
+&i2c0 {
+	/delete-property/ pinctrl-names;
+	/delete-property/ pinctrl-0;
+};
+
 &rmem {
 	/*
 	 * RPi4's co-processor will copy the board's bootloader configuration