Besides Linux 3.18 being closer to allowing the AArch64/ARM64 kernel code to compile under Clang and many ARM/ARM64 Linux kernel improvements, another 3.18 addition for the new 64-bit ARM architecture is the addition of PCI support.
Bjorn Helgaas sent in the Linux 3.18 PCI changes earlier in the week and there's now ARM64 PCI support. The PCI pull request also has new host bridge drivers for the APM X-Gene, Texas Instruments Keystone, and Xilinx AXI. There's also support for allowing PCI devices to be put into D3cold sleep state during system suspends.
More details on the PCI changes for Linux 3.18 can be found via this pull request.