The USB device filesystem can be found under /proc/______/usb/.

The USB device filesystem can be found under /proc/bus/usb/1. This is a virtual filesystem that provides information about the USB devices and buses connected to the system12. It contains files and directories that correspond to the USB host controllers, hubs, and devices12. For example, the following output shows the contents of /proc/bus/usb/ on a system with one USB host controller and two USB devices:

The directories 001 and 002 represent the USB buses, and each contain files that represent the USB devices on that bus. The file devices contains a summary of all the USB devices and their configurations. The file drivers contains a list of the USB drivers and the devices they are bound to12.

The /proc/bus/usb/ filesystem is deprecated and should not be used anymore3. It has been replaced by the /sys/bus/usb/ filesystem, which is a sysfs mount that provides more detailed and structured information about the USB devices and buses3 .

References:

1: USB in a NutShell - Chapter 5 - Linux USB 2: Linux USB FAQ 3: Alternative to /proc/bus/usb/devices - Super User : [What is the difference between /dev/usb, /proc/bus/usb and /sys/bus/usb? - Super User]