The Silicon Labs Si2157 is a hybrid DVB-T, DVB-T2, DVB-C, ATSC, DTMB and QAM Tuner. There are other very similar tuners on that can be used with same Linux driver: Si2146, Si2147, Si2148 and Si2158.
Supported since Linux kernel 3.16 by the si2157.c driver.
A proprietary closed source driver does exist in the drivers shipped with the DVBSky cards.
The Si2148 and Si2158 tuners need firmware.
It is used on the DVBSky T9580, TBS6281, TBS6285, Mystique SaTeCaBiX, PCTV 292e Triplestick and Geniatech T230, for example.