As a part of the research activities in the Embedded Systems – Open Platform Group from Siemens Corporate Technology a group of researchers is working on adding support for the IEEE 802.15.4 Wireless Personal Area Networks to the Linux. The current implementation is neither certified nor even feature complete. However they’d like to present current state of the patchset to the Linux developers community to gain comments, fixes, ideas, etc. This is not yet a pull request, but more like an RFC.
The project page is available at http://apps.sourceforge.net/trac/linux-zigbee with source code of kernel part available from git at http://zigbee-linux.git.sourceforge.net, mirrored for convenience at git://git.kernel.org/pub/scm/linux/kernel/git/lumag/lowpan.git
More info here.