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.

The RTC-related rule causes 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 word of caution: A comma must separate each part of the rule. A rule can span
multiple lines if the newline is escaped by a backslash.