添加rtthread相关代码

riscv/rtthread/components/drivers/fdt/docs/examples.md

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+# fdt示例 #
+
+在`examples`文件夹中存放`bcm2711-rpi-4-b.dtb`和`vexpress-v2p-ca9.dtb`可供测试，如果系统可以从bootloader或其他方式获取到bsp本身的dtb，也可以通过修改示例程序进行测试
+
+## fdt_dump
+```bash
+fdt_dump vexpress-v2p-ca9.dtb
+```
+
+####  示例结果 ####
+```bash
+/dts-v1/;
+
+/ {
+        model = "V2P-CA9";
+        arm,hbi = <0x191>;
+        arm,vexpress,site = <0xf>;
+        compatible = "arm,vexpress,v2p-ca9", "arm,vexpress";
+        interrupt-parent = <0x1>;
+        #address-cells = <0x1>;
+        #size-cells = <0x1>;
+
+        chosen {
+        };
+
+        aliases {
+                serial0 = "/smb@4000000/motherboard/iofpga@7,00000000/uart@9000";
+                serial1 = "/smb@4000000/motherboard/iofpga@7,00000000/uart@a000";
+                serial2 = "/smb@4000000/motherboard/iofpga@7,00000000/uart@b000";
+                serial3 = "/smb@4000000/motherboard/iofpga@7,00000000/uart@c000";
+                i2c0 = "/smb@4000000/motherboard/iofpga@7,00000000/i2c@16000";
+                i2c1 = "/smb@4000000/motherboard/iofpga@7,00000000/i2c@2000";
+        };
+
+...... 省略
+
+        hsb@e0000000 {
+                compatible = "simple-bus";
+                #address-cells = <0x1>;
+                #size-cells = <0x1>;
+                ranges = <0x0 0xe0000000 0x20000000>;
+                #interrupt-cells = <0x1>;
+                interrupt-map-mask = <0x0 0x3>;
+                interrupt-map = <0x0 0x0 0x1 0x0 0x24 0x4 0x0 0x1 0x1 0x0 0x25 0x4 0x0 0x2 0x1 0x0 0x26 0x4 0x0 0x3 0x1 0x0 0x27 0x4>;
+        };
+};
+```
+
+## fdt_test
+```bash
+fdt_test
+```
+
+####  示例结果 ####
+```bash
+name = uart@9000
+reg = <0x9000,0x1000>;
+compatible = "arm,pl011","arm,primecell";
+
+name = cpus
+path = /cpus/cpu@0/
+path = /cpus/cpu@1/
+path = /cpus/cpu@2/
+path = /cpus/cpu@3/
+
+name = user1, lable = v2m:green:user1
+name = user2, lable = v2m:green:user2
+name = user3, lable = v2m:green:user3
+name = user4, lable = v2m:green:user4
+name = user5, lable = v2m:green:user5
+name = user6, lable = v2m:green:user6
+name = user7, lable = v2m:green:user7
+name = user8, lable = v2m:green:user8
+
+/memreserve/    0x0000000000000000 0x0000000000001000;
+
+phandle = <0x9>
+name = bt_pins
+path = /soc/gpio@7e200000/bt_pins/
+brcm,pins = [2d 00]
+```