Benedikt, I just dug into the same ditch as you. Lets combine efforts! look for me on gtalk or skype (cyphunkish on skype, cyphunk at gmail on gtalk). Here was my first dump:
https://www.dvxuser.com/V6/showthread.php?p=1688725
BTW, the .config file of the kernel seems to indicate that the CPU is a SH4 subtype SH7751