The Driver Writer's Guide documents the V4L2 kernel-mode API functions, and provides additional information regarding how to write V4L2 drivers. For instructions on installing V4L2 see the readme file in the V4L2 source archive. You will need to configure your kernel to include Video for Linux as a module, but disable all the v4l drivers since they will not compile after the original v4l header file has been replaced with the new header file. The v4l2samp.tgz file includes a sample device drivers which use no hardware, so you can start writing or porting applications to V4L2 even if you don't have V4L2-supported hardware yet. So far video capture and video output sample drivers are included.
More information is in the readme file included in the archive.
Kernel 2.2.x Video for Linux Two Source Code V4L2 source code for kernel 2.2.x. FTP site for videodev, kernel 2.2.x. Current and previous versions. Configure Video for Linux as a module, and rebuild kernel and kernel modules if necessary. You may want to keep backup copies of these files in case you decide to go back to v4l.