There is a standard protocol for USB webcams. It is called "USB video device class" and usually referred to as UVC or UVCvideo in the Linux kernel:

https://en.wikipedia.org/wiki/USB_video_device_class

Unfortunately not all USB webcams use it yet, but its adoption is growing. Webcams that do use UVCvideo are usually well supported by the Linux kernel. Explicit compatibility list here:

https://www.ideasonboard.org/uvc/