How to understand "using interfaces layered over USB" in this article?

[lx <lxlenovostar@xxxxxxxxx>]

hi all:

      I read this article, but I can't understand this  section：

############################################################

Most USB device drivers should pass these tables to the USB subsystem as
well as to the module management subsystem.  Not all, though: some driver
frameworks connect using interfaces layered over USB, and so they won't
need such a "struct usb_driver".

############################################################

From: https://www.kernel.org/doc/Documentation/usb/hotplug.txt

How to understand "using interfaces layered over USB"?

Thank you.

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