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

This page is about to track every initiative to fully or partially install the system on mobile phones:

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