So you want to build an embedded Linux system?
This article is targeted at embedded engineers who are familiar with microcontrollers but not with microprocessors or Linux, so I wanted to put together something with a quick primer on why you'd want to run embedded Linux, a broad overview of what's involved in designing around application processors, and then a dive into some specific parts you should check out - and others you should avoid - for entry-level embedded Linux systems.
This is some seriously detailed writing, and an amazing starting point for people interested in developing for embedded Linux.