default or selected kernelversion does not have config value CONFIG_DRM_EXYNOS_IOMMU.
Result is shown for kernelversion 6.9.9

CONFIG_DRM_EXYNOS_IOMMU (not configurable)

configname: CONFIG_DRM_EXYNOS_IOMMU

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>DRM_EXYNOS_IOMMU
In linux kernel since version 3.1 (release Date: 2011-10-24)