The best source is the linux man pages but they are somewhat critical to understand for a beginner, Directly programming device drivers is not a easy task. I recommend you to go through pointers and structures through following books
Basic C Books 1. Programming C - Byron gottfried 2. The C Programming Language - Dennis Ritchie
Intermediate Books 1. Pointers on C Kenneth Reek 2. Expert C Programming Deep Secrets - Linden
Coming to device Drivers I have uploaded the Kernel Source documentation in pdf format https://drive.google.com/folderview?id=0B7iRyndFhHldR3hjOHpOZTdKTjA&usp=sharing Youcan download from this link.
Device Drivers Basics (User mode Programming)
Linux Programming interface - Michael Kerrisk
Beginning Linux Programming Wrox Publishers
Device Drivers (Kernel Deleopment) 1. Linux Kernel Development - Robert Love 2. Linux Kernel Internals - m beck
Device Drivers (Driver Programming) 1. Linux Device Drivers - Third Edition (Free Download is available for 2.6 Kernel) 2. Essential Linux Device Drivers - Venkateswaran
For Basic Driver Knowledge Follow this site http://www.tldp.org/LDP/khg/HyperNews/get/devices/devices.html
My Experience is First of all we must gain a sound knowledge on C Programming, mainly Structures and Pointers before going through Driver Programming otherwise it will be bit cumbersome to understand driver programming.
Comming to Startup :-
User space programming
Basics of gcc generating proprocessed, assembler and object files using gcc commands analysis of object files using different object tools, Basic programming in linux, threads(locks, synchronization techniques), signals, processes(fork, exec), timers(Posix). This will help you lot in understanding kernel concepts.
Kernel Programming
Understanding the kernel source tree, different branches and their importance, using ctags and cscope to browse kernel source code, this will help you in kernel source browsing.
Driver Programming
First of all Learn different driver classes, char, block etc.,
Next learn the device protocols, transmission and reception, the product manual is the best source for going through this.
Then start writing the simple char driver for example RTC (a port mapped device), IOAPIC (A memory mapped device), then go to USB, PCI, Network, I2C, SPI etc., if you want the help you can find the skeleton code for all this in kernel source tree.
