With Linux 3.13, ARM's big.LITTLE CPUFREQ driver now supports in-kernel switching between the "big" and "little" cores as part of its performance-scaling. The big.LITTLE implementations we have seen so far are commonly four Cortex-A15 cores making up the "big" performant portion and than four low-power low-performance Cortex-A7 cores when the system is not busy. The CPUFREQ driver for Linux 3.13 now supports in-kernel switching between these different ocres as part of its performance scaling.
The Intel P-State driver in Linux 3.13 will also support Atom "Bay Trail" SoCs as another exciting change going beyond its Sandy Bridge, Ivy Bridge, and Haswell CPU support.
The other big stuff in the Linux 3.13 ACPI and power management pull request is the introduction of the Linux power-capping framework and RAPL driver for run-time average power-limiting. Power-capping paired with the Intel RAPL driver allows systems to limit the power draw of various system components, assuming the hardware supports such capabilities.
Some other good stuff with this update is CPUfreq for the Apple iMac G5, CPUfreq for Calxeda's "Midway" ECX-2000 platform, and many other fixes and updates.
Last but not least the ACPICA code was updated to match upstream 20130927 with ACPI power management now being supported for the I2C and SPI buses.
While Linus is expected to open the Linux 3.13 kernel merge window over the weekend, this ACPI/PM pull request can be found already as of this morning on the kernel mailing list.