write a new built in type

Hi all,
I with to write a new builtin type, I seen that what I have to do is:

1) ad on pgsql/src/include/utils/builtins.h
the signature for my function that will manipulate my
type

2) ad on pgsql/src/backend/utils/adt
a new file my_type.c
with the implementation of all function inserted in the file
at point 1

and what else ? For example how may I define the name for my new type ?

Regards
Gaetano Mendola