add_feed() WordPress Function

function add_feed( $feedname, $function ) {
	global $wp_rewrite;

	if ( ! in_array( $feedname, $wp_rewrite->feeds, true ) ) {
		$wp_rewrite->feeds[] = $feedname;
	}

	$hook = 'do_feed_' . $feedname;

	// Remove default function hook.
	remove_action( $hook, $hook );

	add_action( $hook, $function, 10, 2 );

	return $hook;
}
Uses	Description
wp-includes/plugin.php:remove_action()	Removes a callback function from an action hook.
wp-includes/plugin.php:add_action()	Adds a callback function to an action hook.