Purpose of rules file:

Most of the rules installed by Udev itself create devices with the correct
properties.  This file contains rules that have not been merged upstream yet.

Description of rules:

By default, Udev creates device nodes with UID 0, GID 0, and permissions 0660.

ISDN-related devices should be owned by the 'dialout' group, hence the following
rule (and similar):

KERNEL=="ippp[0-9]*", GROUP="dialout"

The RTC-related rules cause the setclock bootscript to be run as soon as the
RTC device has been created by Udev, meaning that times in log files, for
example, are as accurate as possible as quickly as possible.

A final word of caution: Any particular rule must be written on one line, and a
comma must separate each part of the rule.