A large amount of TLDP is obsolete. The howtos are usually good, but many of them are seriously out of date and contain advice that is now counterproductive. Check the date of each howto before deciding whether to read and trust it.
Even back in the day, howtos were not to be followed blindly. For example, many howtos start with instructions on compiling some software which, by the time most readers read the document, was bundled in distributions.
I'm not aware of any similar project that's more up-to-date. The current trend is towards community-edited guides, wiki-style. You get the benefit of more diverse experiences, but you lose the trust that you may (but then again, may not) put in a single author, and information is often spread over more pages and less easy to get at offline. Also remember that information in wikis can get obsolete too.
I don't think TLDP is a worthwhile resource for learning Linux administration nowadays. 10 years ago, yes, but not now. I recommend starting with a book, then exploring the wiki for your distribution (most have one), exploring /etc, reading Unix & Linux Stack Exchange, skimming newgroups... Refer to howtos if you find recent ones on a subject that interests you.
Sorry for repeating but take a look to Nano-X sources.
git clone git://microwindows.org/microwin
In particular take a look to the files:
drivers/kbd_tty.c
drivers/scr_fb.c
What is done in the tty driver is very similar to what Xorg does, and The devfb driver is a very simple and clean implementation.
Linux's devfb frame buffers mostly rely on ioctl (eg: to set/get resolution) and mmap (to raw write/read pixels).
devfb is just one (easy and a bit more portable on linux) way to access the graphic hardware.
Xorg drivers instead are composed by a kernel driver and a Xorg user space interface between the driver and Xorg itself, and what happen between kernel and user side is really implementation-dependant (there isn't a standard).
You can also take a look to SDL or Directfb but Nano-X is the cleanest/easy and a display server itself, so probably could help you on other question that you'll surely meet.
Best Answer
man 7 signal