Improve sysnet_read_config() documentation.

policy/modules/system/sysnetwork.if

@@ -218,6 +218,27 @@ interface(`sysnet_setattr_config',`
 ## <summary>
 ##	Read network config files.
 ## </summary>
+## <desc>
+##	<p>
+##	Allow the specified domain to read the
+##	general network configuration files.  A
+##	common example of this is the
+##	/etc/resolv.conf file, which has domain
+##	name system (DNS) server IP addresses.
+##	Typically, most networking processes will
+##	require	the access provided by this interface.
+##	</p>
+##	<p>
+##	Higher-level interfaces which involve
+##	networking will generally call this interface,
+##	for example:
+##	</p>
+##	<ul>
+##		<li>sysnet_dns_name_resolve()</li>
+##		<li>sysnet_use_ldap()</li>
+##		<li>sysnet_use_portmap()</li>
+##	</ul>
+## </desc>
 ## <param name="domain">
 ##	<summary>
 ##	Domain allowed access.