Documentation: Add timers/timers-howto.txt

Documentation: Add timers/timers-howto.txt

This file seeks to explain the nuances in various delays;
many driver writers are not necessarily familiar with the
various kernel timers, their shortfalls, and quirks. When
faced with

ndelay, udelay, mdelay, usleep_range, msleep, and msleep_interrubtible

the question "How do I just wait 1 ms for my hardware to
latch?" has the non-intuitive "best" answer:
	usleep_range(1000,1500)

This patch is followed by a series of checkpatch additions
that seek to help kernel hackers pick the best delay.

Signed-off-by: Patrick Pannuto <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Randy Dunlap <[email protected]>
Cc: Andrew Morton <[email protected]>
LKML-Reference: <1280786467[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>