dm: usb: Add tests for the USB uclass

This adds a simple test for probing and a functional test using the flash
stick emulator, which tests a large chunk of the USB stack.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/test/dm/test.dts b/test/dm/test.dts
index 0ab0916..d0c40be 100644
--- a/test/dm/test.dts
+++ b/test/dm/test.dts
@@ -20,6 +20,9 @@
 		testfdt8 = "/a-test";
 		eth0 = "/eth@10002000";
 		eth5 = &eth_5;
+		usb0 = &usb_0;
+		usb1 = &usb_1;
+		usb2 = &usb_2;
 	};
 
 	uart0: serial {
@@ -186,4 +189,42 @@
 		fake-host-hwaddr = <0x00 0x00 0x66 0x44 0x22 0x22>;
 	};
 
+	usb_0: usb@0 {
+		compatible = "sandbox,usb";
+		status = "disabled";
+		hub {
+			compatible = "sandbox,usb-hub";
+			#address-cells = <1>;
+			#size-cells = <0>;
+			flash-stick {
+				reg = <0>;
+				compatible = "sandbox,usb-flash";
+			};
+		};
+	};
+
+	usb_1: usb@1 {
+		compatible = "sandbox,usb";
+		hub {
+			compatible = "usb-hub";
+			usb,device-class = <9>;
+			hub-emul {
+				compatible = "sandbox,usb-hub";
+				#address-cells = <1>;
+				#size-cells = <0>;
+				flash-stick {
+					reg = <0>;
+					compatible = "sandbox,usb-flash";
+					sandbox,filepath = "testflash.bin";
+				};
+
+			};
+		};
+	};
+
+	usb_2: usb@2 {
+		compatible = "sandbox,usb";
+		status = "disabled";
+	};
+
 };