Ok some specific examples of missing changes or stuff that only the 5422 supports:

Secure OS Control does not support the 5420 because we do not have HMP big.little enabled
https://github.com/kumajaya/android_kernel_samsung_universal5422/tree/ad41104d43e6470f8d4880d65b259dc7b903cc0d/drivers/gud/gud-exynos5422/sec-os-ctrl

The header requires HMP to be enabled
https://github.com/kumajaya/android_kernel_samsung_universal5422/blob/ad41104d43e6470f8d4880d65b259dc7b903cc0d/drivers/gud/gud-exynos5422/MobiCoreDriver/platforms/EXYNOS_5422_STD/platform.h#L31

5422 removes support for setting the types of ram as well as changing the length of the physical addresses for said ram
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/Mci/mcifc.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/README.android

The 5422 version completely remove support for the provisioning agent api (PaApi)
https://github.com/CM-Tab-S/android_hardware_samsung_slsi-cm_exynos5420/tree/cm-13.0/mobicore/daemon/PaApi

Legal problem with some of the files in the newer version they all say its confidential and proprietary where as the older hardkernel ones are not
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcContainer.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcDriverId.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcLoadFormat.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcRootid.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcSo.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcSpid.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcSuid.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcUuid.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcVersionHelper.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/common/MobiCore/inc/mcVersionInfo.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/ClientLib/public/GP/tee_error.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/ClientLib/public/GP/tee_internal_api_impl.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/ClientLib/public/GP/tee_type.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/ClientLib/public/GP/uuid_attestation.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/ClientLib/public/Windows/t-base_client_api.def
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/Daemon/FSD/public/dci.h
http://review.cyanogenmod.org/#/c/141723/7/mobicore/daemon/Daemon/FSD/public/drSecureStorage_Api.h