All Lightroom5 users and Cloud-Subscribers have access to Lightroom 5.3 update with some of the new camera & lens support along with some bug-fixes. As always, this update can be applied through the application's update mechanism.
So let us quickly share the new cameras being supported in this update -
Canon EOS M2
Canon PowerShot S120
Casio EX-10
Fujifilm XQ1
Fujifilm X-E2
Nikon 1 AW1
Nikon Coolpix P7800
Nikon Df
Nikon D610
Nikon D5300
Nokia Lumia 1020
Olympus OM-D E-M1
Olympus STYLUS 1
Panasonic DMC-GM1
Pentax K-3
Phase One IQ260
Phase One IQ280
Sony A7 (ILCE-7)
Sony A7R (ILCE-7R)
Sony DSC-RX10
Tethering is not supported for all the cemaras, so this time teathering workflows are supported for Canon EOS Rebel T4i , EOS 650D & EOS Kiss X6i.
List of new lenses supported can be checked at - http://blogs.adobe.com/lightroomjournal/2013/12/lightroom-5-3-now-available.html
Above link has also a list of issues fixed in Lightroom 5.3 . So just update and enjoy working with your new cameras & lenses, along with some improved workflows.