overlays: mcp23017: Support the MCP23008

Add an 'mcp23008' parameter to enable support for the MCP23008 device.

See: #2818

Signed-off-by: Phil Elwell <[email protected]>

Author: Phil Elwell

arch/arm/boot/dts/overlays/README

@@ -1212,6 +1212,8 @@ Params: gpiopin                 Gpio pin connected to the INTA output of the
 
         addr                    I2C address of the MCP23017 (default: 0x20)
 
+        mcp23008                Configure an MCP23008 instead.
+
 
 Name:   mcp23s17
 Info:   Configures the MCP23S08/17 SPI GPIO expanders.

arch/arm/boot/dts/overlays/mcp23017-overlay.dts

@@ -44,11 +44,19 @@
 			};
 		};
 	};
-	
+
+	fragment@3 {
+		target = <&mcp23017>;
+		__dormant__ {
+			compatible = "microchip,mcp23008";
+		};
+	};
+
 	__overrides__ {
 		gpiopin = <&mcp23017_pins>,"brcm,pins:0",
 				<&mcp23017>,"interrupts:0";
 		addr = <&mcp23017>,"reg:0";
+		mcp23008 = <0>,"=3";
 	};
 };