There are many posts in the forums about Windows XP support in ConfigMgr 2012 R2.
Windows XP SP3 is still a supported as a ConfigMgr 2012 R2 client, and both ConfigMgr 2012 SP1 CU3 and ConfigMgr 2012 R2 can deploy everything from Windows XP to Windows 8.1
However, to deploy Windows XP SP3 with either ConfigMgr 2012 SP1 or ConfigMgr 2012 R2, you need add a WinPE 3.1 boot image from a separately installed Windows 7 AIK.
On a side note, it was actually supported to deploy Windows XP with ConfigMgr 2012 SP1 using a WinPE 4.0 boot image (from ADK 8.0), but since already ConfigMgr 2012 SP1 CU2 added support to use WinPE 3.1 boot images, that's the recommended path also when using ConfigMgr 2012 SP1.
Note: MDT 2013 does Not support Windows XP deployments, but ConfigMgr 2012 R2 does.