There is no reason that Smartphone do not support Debian also.

This page is about to track every initiative to fully or partialy install the system on mobiles :

Hardware

Projects

Smartphone tasks is handled by FSO team :

http://wiki.debian.org/Teams/DebianFSO

Openmoko's FreeRunner is so far the device best supported :

Nokia's maemo is based on debian :

Same as mer the community based fork :

Upcoming distro ?MeeGo may be open to accept debian (re)built packages too :

Also there is an ugly alternative to install debian is to run it in a chroot dir :

Misc :