SQL Server AlwaysOn from multiple origins to a single secondary replica server
It is possible, provided that:


all servers run the same post 2012 version, preferably 2014 and all patched to the same SP/CU.
all servers are licensed to Enterprise Edition
all servers are in the same domain, or a within domains that trust each other


Perhaps you are interested in Transactional Replication instead? This would support a heterogeneous configuration (2008, 2012, 2014), crossing domain boundaries via mirrored NT accounts, does not require Enterprise licensing everywhere. You need to explicitly set up the 'published articles' (ie. what tables get replicated).