Intel Broadwell processors introduce a new RDSEED CPU instruction that is used as a pseudo-random number generator (PRNG). The RDRAND instruction (also known as Bull Mountain) that was introduced with Ivy Bridge CPUs is considered by the US NIST as a cryptographically secure pseudorandom number generator. The RDSEED instruction meanwhile is considered a non-deterministic random bit generator in compliance with NIST's SP 800-90 B and C.
RDSEED yields a true random number generator and is intended to be used by software that have an existing pseudo-random number generator so you can use RDSEED as its seed input. With the Linux 3.15 kernel, the RDSEED instruction is supported with Broadwell hardware for seeding /dev/random.
The random pull request for the Linux 3.15 kernel can be found on the kernel mailing list.