/proc/823/root/sys/class/usb_device/usbdev2.1/device/2-0%3A1.0/usb_endpoint%3Ausbdev2.1_ep81/subsystem/

../
usbdev1.1_ep00/
usbdev1.1_ep81/
usbdev2.1_ep00/
usbdev2.1_ep81/