CONFIG_ARCH_MEDIATEK is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Mediatek MT6589 SoC

modulename: mediatek.ko

and/or

irq-mtk-sysirq.ko

configname: CONFIG_ARCH_MEDIATEK

Linux Kernel Configuration
└─>Mediatek MT6589 SoC
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Support for Mediatek Cortex-A7 Quad-Core-SoC MT6589.

source code:
arch/arm/mach-mediatek/mediatek.c

depends
 or CONFIG_ARCH_MULTI_V7

is selected by
CONFIG_MTK_PMIC_WRAP