The Ralink RT5390 is an 802.11 b/g/n chipset that bears a PCI Express 1.1 interface. The product brief for the RT5390 on the Ralink web-site does advertise Linux support along side Windows and Mac OS X support.
Hitting the rt2x00 mailing list yesterday was a set of patches from a Ralink engineer providing the said support to this open-source driver.
This is not the first time that Ralink has provided open-source Linux driver code, but in the past they have just done tar-ball drops rather than actively engaging with the upstream Linux kernel community.
This achievement was noted by Greg Kroah-Hartman on his blog. Novell, the Linux Driver Project, and Greg were involved in pushing for these Ralink Linux driver improvements.