To be able to build for device OpenEmbedded have to know it, so machine config file need to be written. All those configs are stored in /conf/machine/ directory.
As usual some variables are required:
TARGET_ARCH which describe which CPU architecture does machine use.
MACHINE_FEATURES which describe which features device has. More about it in task-base section.
PREFERRED_PROVIDER_virtual/kernel has to point into proper kernel recipe for this machine.
Next kernel recipe needs to be added.