Len Brown of Intel sent in a few basic tweaks for the idle drivers at the end of the Linux 3.17 merge window. One commit disables Bay Trail's Core and Module C6 auto-demotion while the other main patch adds Broadwell support to the intel_idle driver.
The patch for Broadwell intel_idle support by Len explains, "Broadwell (BDW) is similar to Haswell (HSW), the preceding processor generation. Currently, the only difference in their C-state tables is that PC3 max exit latency is 33usec on HSW and 40usec on BDW."
The pull request can be found on the kernel mailing list. Intel started shipping their Broadwell-Y processors and you can expect to find them in ultra-portables by this holiday season and there should be great Linux support for this successor to Haswell.