CONFIG_RPMSG (not configurable)

modulename: rpmsg_core.ko

and/or

virtio_rpmsg_bus.ko

configname: CONFIG_RPMSG

Linux Kernel Configuration
└─>Device Drivers
└─>Rpmsg drivers (EXPERIMENTAL)
└─>RPMSG
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:

depends
CONFIG_EXPERIMENTAL

is selected by
CONFIG_QCOM_APR