PS2:EE Serial Output

WIP!

TODO: Document the installation of the EmotionEngine Serial output (EE SIO) hardware modification used for debugging homebrew.

Links:

• https://www.ps2-home.com/forum/viewtopic.php?t=4828
• https://web.archive.org/web/20070314223535/http://www.kanshima.net/mirrors/ee-sio/ps2-ee-sio.html
• https://pdfcoffee.com/ps2eesioinfo-pdf-free.html