xenix system V tty drivers

[Saeed Talebbeik]

Is there any source ( books, code, etc.) that specifically addresses how to
write tty device drivers. I have heard that writing the line descipline routine
are very difficult and time consuming and you are better off using the functions
already provided in the kernel for that. The Santa Cruz Operations offers a 
course which is good but first it costs almost 1500 bucks and second it is 
offered on February 25 which is too late. I will appreciate any help or 
suggestions .
                                 Thanks ,
                                <<<saeed>>>