This is a 4,8 or 12 port SATA RAID controller. Recent linux kernels (since 2.4.20-something) have native support for these controllers, under the SCSI low-level driver section.
This is particularly the 9x00 SATA controllers. The 7x00 amd 8x00 (PATA and SATA) controllers are a different model, and a different driver.
Uses the 'twe' driver in FreeBSD.