The Gentoo Handbook tells you to install the /dev fs during the manual configuration of the kernel. However, as of the 2.6 kernel this file system has become obsolete and there is no reason to install it. The handbook needs updating for the difference between 2.4 and 2.6 in this respect.
AFAIK the transition is not smooth enough atm. It's not just enough to change /dev to /udev in the kernel config.
uhh i dont know what you mean by '/dev' and '/udev' but i'm going to assume you mean 'devfs' and 'udev' ...
Gentoo doesnt take the route many others do by creating a separate /udev directory ... but Sergey is correct in saying that simply disabling devfs is all you have to do
what *could* be done is mention the udev guide here:
*** Bug 54763 has been marked as a duplicate of this bug. ***
I'll mark this as later as devfs will go away eventually, I suppose.
Closing this bug as per Josh's request in gentoo-doc's ML.