设备树中那些节点会被转换为内核里的platform

设备树中的节点有些能被转换为内核里的platform_device，有些不能：

A. 根节点下含有compatile属性的子节点，会转换为platform_device;

B. 含有特定compatile属性的节点的子节点，会转换为platform_device,

如果一个节点的compatile属性，它的值是这4者之一：“simple-bus”,“simple-mfd”,“isa”,“arm,amba-bus”, 那么它的子结点(需含compatile属性)也可以转换为platform_device。

C. 总线I2C、SPI节点下的子节点：不转换为platform_device, 某个总线下到子节点，应该交给对应的总线驱动程序来处理, 它们不应该被转换为platform_device。

举例：

各个gpio节点在根节点下的soc节点下的aips1节点：

aips1节点的compatile就包含 simple-bus，所以gpio节点就会被转换成platform_device，gpio子系统的驱动实现就是使用的platform，设备树如下：

	soc {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "simple-bus";
		interrupt-parent = <&gpc>;
		ranges;

		...
        

		aips1: aips-bus@02000000 {
			compatible = "fsl,aips-bus", "simple-bus";
			#address-cells = <1>;
			#size-cells = <1>;
			reg = <0x02000000 0x100000>;
			ranges;


			...


			gpio1: gpio@0209c000 {
				compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
				reg = <0x0209c000 0x4000>;
				interrupts = <GIC_SPI 66 IRQ_TYPE_LEVEL_HIGH>,
					     <GIC_SPI 67 IRQ_TYPE_LEVEL_HIGH>;
				gpio-controller;
				#gpio-cells = <2>;
				interrupt-controller;
				#interrupt-cells = <2>;
			};

			gpio2: gpio@020a0000 {
				compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
				reg = <0x020a0000 0x4000>;
				interrupts = <GIC_SPI 68 IRQ_TYPE_LEVEL_HIGH>,
					     <GIC_SPI 69 IRQ_TYPE_LEVEL_HIGH>;
				gpio-controller;
				#gpio-cells = <2>;
				interrupt-controller;
				#interrupt-cells = <2>;
			};

			gpio3: gpio@020a4000 {
				compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
				reg = <0x020a4000 0x4000>;
				interrupts = <GIC_SPI 70 IRQ_TYPE_LEVEL_HIGH>,
					     <GIC_SPI 71 IRQ_TYPE_LEVEL_HIGH>;
				gpio-controller;
				#gpio-cells = <2>;
				interrupt-controller;
				#interrupt-cells = <2>;
			};

			gpio4: gpio@020a8000 {
				compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
				reg = <0x020a8000 0x4000>;
				interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>,
					     <GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH>;
				gpio-controller;
				#gpio-cells = <2>;
				interrupt-controller;
				#interrupt-cells = <2>;
			};
        ...

原文链接：https://blog.youkuaiyun.com/thisway_diy/article/details/105394053