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 <ppannuto@codeaurora.org>
Cc: apw@canonical.com
Cc: corbet@lwn.net
Cc: arjan@linux.intel.com
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <1280786467-26999-3-git-send-email-ppannuto@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>