BoardConfig.mk:
TARGET_CPU_SMP := true # build flag for dalvik/vm;dalvik/dexopt;bionic/libstdc++;bionic/libc
and system/core/libcutils
ARCH_ARM_HAVE_TLS_REGISTER := true # build flag for bionic/linker;bionic/libc
and framework/base/opengl
TARGET_CORTEX_CACHE_LINE_32 := true # build flag for bionic/libc

treat this device as a qcom device with BOARD_USES_QCOM_HARDWARE := true

set the GPS LOC API
BOARD_VENDOR_QCOM_GPS_LOC_API_AMSS_VERSION := 50000
BOARD_VENDOR_QCOM_GPS_LOC_API_HARDWARE := default

device_AD683G.mk:

add permission xmls from frameworks/base/data/etc
add PRODUCT_COPY_FILES for prebuilt files
add PRODUCT_PACKAGES flag from gps defined at BoardConfig.mk
add kernel headers from somewhere in the internet, plus
TARGET_SPECIFIC_HEADER_PATH
to include them
adds graphics flags and product packages, also audio product packages
adds common global cflags to pass the device as msm7x27a