Android M was unveiled at Google I/O 2015 and it is currently only available for selected Nexus devices as a Developer Preview. Sony has taken a step up to make the AOSP preview build of Android M for selected Xperia devices. It is now available for you to download and try if you have a selected Sony Device, part of the Open Device program.
Sony has put out the necessary binaries to compile a working ROM for quite a few of its handsets and tablets, as well as a comprehensive guide through the process. However, there is an important note to be made. When Sony says it’s for development purposes, it definitely means it. Not only do you have to compile your own ROM, but it still has a lot of missing parts, most notably the camera and modem, which are not implemented yet.
Currently supported devices are,
Xperia™ Z3 Compact
Xperia™ Z3 Tablet Compact
Xperia™ Z2 Tablet
Xperia™ Z1 Compact
Xperia™ Z Ultra
Xperia™ T2 Ultra
This makes the end product all but pointless for everyday use and thus it’s indeed meant for testing and debugging only. However, it is also worth mentioning that such source code releases have usually lead to some quick work from the modding community, so it wouldn’t really surprise us if crude, working ROMs start popping up for various Sony devices soon.
The tools, binaries and guide are all available here. If you are interested, check it out and give it a go!