Add network-lookup-address-info description

* doc/lispref/processes.texi (Misc Network): Document
  network-lookup-address-info.

doc/lispref/processes.texi

@@ -2923,6 +2923,21 @@ If the vector does not include the port number, @var{p}, or if
 @code{:@var{p}} suffix.
 @end defun
 
+@defun network-lookup-address-info name &optional family
+This function is used to perform hostname lookups on @var{name}, which
+is expected to be an ASCII-only string, otherwise an error is
+signaled. Call @code{puny-encode-domain} on @var{name}
+first if you wish to lookup internationalized hostnames.
+
+If successful it returns a list of Lisp representations of network
+addresses (without port numbers), otherwise it returns @code{nil}.
+
+By default both IPv4 and IPv6 lookups are attempted.  The optional
+argument @var{family} controls this behavior, specifying the symbol
+@code{ipv4} or @code{ipv6} restricts lookups to IPv4 and IPv6
+respectively.
+@end defun
+
 @node Serial Ports
 @section Communicating with Serial Ports
 @cindex @file{/dev/tty}