Wolfgang,
thanks a lot for your great help. It's really amazing.
As Marcin said, getting access to some more boards/units would be useful, especially if they have JTAG access and even if some of them might not be fully functional. Charger/USB cable are definitely reqired, all the other parts are more or less optional.
Schematics would also most definitely be great. PCB pictures might be useful as a replacement if no schematics are available.
Sad to hear that it is already end of life, but good to know that there might be more MT6235 based designs that have JTAG exposed.
Cheers from Luzern/Switzerland, Harald