How to set a package to be included by make defconfig

I'd like to get my package included in the final .config with make defconfig, but it seems that there is no such facility in define Package/my-package. I suppose it would be something like this:

define Package/FOO_BAR
  DEFAULT := y
  SECTION := xxx
endef

or

config FOO_BAR
  bool "A foo and a bar"
  default y