CONFIG_CAVIUM_OCTEON_SOC is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Cavium Networks Octeon SoC based boards

modulename: pci-octeon.ko

and/or

msi-octeon.ko

configname: CONFIG_CAVIUM_OCTEON_SOC

System type
└─>Cavium Networks Octeon SoC based boards
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This option supports all of the Octeon reference boards from Cavium
Networks. It builds a kernel that dynamically determines the Octeon
CPU type and supports all known board reference implementations.
Some of the supported boards are:
EBT3000
EBH3000
EBH3100
Thunder
Kodama
Hikari
Say Y here for most Octeon reference boards.

source code:
arch/mips/pci/

is selected by
CONFIG_OCTEON_ETHERNET