How to install PostgreSQL 9.2 with PostGIS 2.0 on Ubuntu 11.10 (or higher)?

I have read this question: https://dba.stackexchange.com/questions/25033/install-postgis-v2-for-postgresql-v9-2, but it didn't resolve my problem.

I added the PostgreSQL backports PPA and installed the postgresql-9.2 package, but there is no package for PostGIS.