The linux-next tree is the holding area for patches aimed at the next kernel merge window. If you're doing bleeding edge kernel development, you may want to work from that tree rather than Linus Torvalds' mainline tree.
If you haven't already done so, first clone a copy of the mainline Linux Git repository:
$ git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
# or: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Cloning into 'linux'...
...
Then add a remote tracking branch for linux-next:
$ cd linux
$ git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
# or: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
Fetch linux-next plus tags
$ git fetch linux-next
...
$ git fetch --tags linux-next
...
Update linux-next:
$ git checkout master # to be safe
...
$ git remote update
...
List (recent) linux-next tags:
$ git tag -l "next-*" | tail
next-20140612
next-20140613
next-20140616
next-20140617
next-20140618
next-20140619
next-20140620
next-20140623
next-20140624
next-20140625
Choose the linux-next version that you will work from, and create a local branch based on that version:
$ git checkout -b my_local_branch next-20140625
Switched to a new branch 'my_local_branch'