Creation of separate versions of design and web-templates for users, who go on your website via mobile devices, can resolve the problem with correct display and work of the site on smartphones and tablets.
This solution is not that omni-purpose, but does have its own substantial advantage without a doubt and is the most popular in mobile development nowadays.
Мit is relatively easier and cheaper to develop a mobile version of a site. There is no need to interfere somehow with the work of desktop site, change it. Mobile versions are integrated with CMS of the site directly and fully, and all the changes made to main version, automatically move to mobile one.
Search engines can easily differentiate mobile versions from non-mobile. That is why under correct SEO set-up, there won’t be any problems with copies and SEO.