Hi Lance,
In order to build the kernel via yocto system, you should need to know about the bitbake and open embedded build system. Even I am not an expert but i can give you a clue.
For example, if the ../mcsdk/sources/meta-ti/recipes-kernel/linux/linux-keystone_3.10.bb is used for kernel building then corresponding defconfig file should be available in ../mcsdk/sources/meta-ti/recipes-kernel/linux/linux-keystone-3.10/ directory.
Most of the linux build recipe uses as above, but you shall read bitbake(bb) files to know from where/which defconfig file is used by yocto to build linux kernel.
Also bitbake user guide. I hope this helps.
Thanks.