eldk: compiling linux for custom hardware

I'm going to compile embedded power pc linux for a custom hardware.
I use the Denx ELDK.
The Linux Kernel configuration (make menuconfig) asks what machine type
to compile Linux for.
So I have the problem that I do not know which option to choose ("none"
is not an option in the dialogue) and that I also do not know what
choosing one of the existing options actually changes behind the scenes.
I'd like a Linux to drop out that supports my MPC875 chip, works with
the LXT 970A ethernet PHY chip and (if possible) the ISP1301
USB-on-the-go USB chip the board has and supports a serial terminal via
SCC4 via the RXD4/TXD4 signals.

Any hint will be appreciated,

best regards,

Peter Asemann