Google recently explained how to handle multilingual situations like this. Their example shows the usage of subdomains but you can use domains as well:
<link rel="alternate" hreflang="en" href="http://www.company.com/" />
<link rel="alternate" hreflang="es-ES" href="http://company.es/" />
<link rel="alternate" hreflang="es-MX" href="http://companymx.es/" />
As far as mobile websites go, they covered that here.
A very common question we see is: Does it matter if the different
types of content are served from the same URL or from different URLs?
For example, some websites have www.example.com as the URL desktop
browsers are meant to access and have m.example.com or wap.example.com
for the different mobile devices. Other websites serve all types of
content from just one URL structure like www.example.com.
For Googlebot and Googlebot-Mobile, it does not matter what the URL
structure is as long as it returns exactly what a user sees too. For
example, if you redirect mobile users from www.example.com to
m.example.com, that will be recognized by Googlebot-Mobile and both
websites will be crawled and added to the correct index. In this case,
use a 301 redirect for both users and Googlebot-Mobile.
If you serve all types of content from www.example.com, i.e. serving
desktop-optimized content or mobile-optimized content from the same
URL depending on the User-agent, this will also lead to correct
crawling by Googlebot and Googlebot-Mobile. This is not considered
cloaking by Google.
It is worth repeating that regardless of URL structure, you must
correctly detect the User-agent as given by your users and
Googlebot-Mobile, and serve both the same content. Don’t forget to
keep the default content, the desktop-optimized content, for when an
unknown User-agent requests it.
