Fantastic job, congratulations
We knew since the beginning that it would be possible, but nobody was sufficiently interested in doing that work - until now.
Good thing to be posting on this board as well.
Mainlining the port is an absolute must for long-term maintenance, and for a 32-bit ARM9 platform, this does indeed require using DT: it already was a requirement when the Nspire Linux port was mainlined years ago, as Arnd Bergmann indicated when replying to https://lkml.org/lkml/2013/4/4/113
. The tools associated to Nspire Linux may save you some time with that task: there's a DTB loader in there.
It's alright to make a bit more progress on a non-DT kernel for now, but you'll soon be spending time on code you'll have to redo for using DT, so you shouldn't wait much