We didn't expect such way of use. In this case there is workaround only based on changing of "Mobile - Domains" plugin.
Try to replace text of function onDeviceDetection in the file plugins/mobile/domains.php with the following:
function onDeviceDetection(&$MobileJoomla_Settings, &$MobileJoomla_Device)
{
if($MobileJoomla_Settings['domains'] == '1')
{
$parsed = parse_url(JURI::base());
$path = isset($parsed['path']) ? $parsed['path'] : '';
$http = isset($parsed['scheme']) ? $parsed['scheme'] : 'http';
$domain_xhtml = $MobileJoomla_Settings['xhtmldomain'];
if($domain_xhtml && $_SERVER['HTTP_HOST'] == $domain_xhtml)
{
if(!$MobileJoomla_Device['markup'])
$MobileJoomla_Device['markup'] = 'xhtml';
$config =& JFactory::getConfig();
$config->setValue('config.live_site', $http.'://'.$domain_xhtml.$path);
}
elseif($MobileJoomla_Device['markup']!=='')
{
global $mainframe;
if($MobileJoomla_Settings['xhtmlredirect'] && $domain_xhtml)
$mainframe->redirect($http.'://'.$domain_xhtml.$path);
}
}
}
After the modification set
General Settings / Domain (multisite) support : Yes
Smartphone (XHTML-MP/WAP2.0) Domain / Domain name : mobile.site.com
Smartphone (XHTML-MP/WAP2.0) Domain / Redirect to domain : Yes (if you need it)
