For a developer like you working on and looking to contribute code upstream, you must work on the very latest version of the Linux kernel code base. Well, there are fine gradations of the latest version within the kernel community. As mentioned earlier, the linux-next tree, and some specific branch or tag within it, is the one to work on for this purpose.
In this book, though, we do not intend to delve into the gory details of setting up a linux-next tree. This process is already very well documented and we would prefer not to merely repeat instructions (see the Further reading section for detailed links). The detailed page on how exactly you should clone a linux-next tree is here: Working with linux-next, https://www.kernel.org/doc/man-pages/linux-next.html, and, as mentioned there, the linux-next tree, http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git, is the holding area for patches aimed at the next...