overlays: added sc16is750 UART over I2C (#1617)

Author: staroselskii

arch/arm/boot/dts/overlays/Makefile

@@ -74,6 +74,7 @@ dtbo-$(RPI_DT_OVERLAYS) += rpi-ft5406.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += rpi-proto.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += rpi-sense.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += rra-digidac1-wm8741-audio.dtbo
+dtbo-$(RPI_DT_OVERLAYS) += sc16is750-i2c.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += sc16is752-spi1.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += sdhost.dtbo
 dtbo-$(RPI_DT_OVERLAYS) += sdio.dtbo

arch/arm/boot/dts/overlays/README

@@ -927,6 +927,16 @@ Load:   dtoverlay=rra-digidac1-wm8741-audio
 Params: <None>
 
 
+Name:   sc16is750-i2c
+Info:   Overlay for the NXP SC16IS750 UART with I2C Interface
+        Enables the chip on I2C1 at 0x48. To select another address,
+        please refer to table 10 in reference manual.
+
+Load:   dtoverlay=sc16is750-i2c,<param>=<val>
+Params: int_pin                 GPIO used for IRQ (default 24)
+        addr                    Address (default 0x48)
+
+
 Name:   sc16is752-spi1
 Info:   Overlay for the NXP SC16IS752 Dual UART with SPI Interface
         Enables the chip on SPI1.

arch/arm/boot/dts/overlays/sc16is750-i2c-overlay.dts

@@ -0,0 +1,37 @@
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";
+
+	fragment@0 {
+		target = <&i2c_arm>;
+		__overlay__ {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			status = "okay";
+
+			sc16is750: sc16is750@48 {
+				compatible = "nxp,sc16is750";
+				reg = <0x48>; /* address */
+				clocks = <&sc16is750_clk>;
+				interrupt-parent = <&gpio>;
+				interrupts = <24 2>; /* IRQ_TYPE_EDGE_FALLING */
+				#gpio-cells = <2>;
+
+				sc16is750_clk: sc16is750_clk {
+					compatible = "fixed-clock";
+					#clock-cells = <0>;
+					clock-frequency = <14745600>;
+				};
+			};
+		};
+	};
+
+
+	__overrides__ {
+		int_pin = <&sc16is750>,"interrupts:0";
+		addr = <&sc16is750>,"reg:0";
+	};
+
+};