====== configs and overlays ======

[[https://docs.zephyrproject.org/latest/develop/application/index.html#important-build-system-variables|Important Build System Variables]]

===== configs =====

  * ''CONF_FILE'': Indicates the name of one or more Kconfig configuration fragment files. Multiple filenames can be separated with either spaces or semicolons. Each file  includes Kconfig configuration values that override the default configuration values.
  * ''EXTRA_CONF_FILE'': Additional ''Kconfig'' configuration fragment files. Multiple filenames can be separated with either spaces or semicolons. This can be useful in order to leave ''CONF_FILE'' at its default value, but “mix in” some additional configuration options.
    * ''EXTRA_CONF_FILE'' replaces ''OVERLAY_CONFIG''
    * Example: ''-DEXTRA_CONF_FILE=overlay-bt_ll_sw_split.conf''


===== device trees =====

  * ''DTC_OVERLAY_FILE'' One or more devicetree overlay files to use. Multiple files can be separated with semicolons. See [[https://docs.zephyrproject.org/latest/build/dts/howtos.html#set-devicetree-overlays|Set devicetree overlays]] for examples and [[https://docs.zephyrproject.org/latest/build/dts/intro.html#devicetree-intro|Introduction to devicetree]] for information about devicetree and Zephyr.
  * ''EXTRA_DTC_OVERLAY_FILE'': Additional devicetree overlay files to use. Multiple files can be separated with semicolons. This can be useful to leave ''DTC_OVERLAY_FILE'' at its default value, but “mix in” some additional overlay files.

===== others =====

  * ''OVERLAY_CONFIG''
  * ''EXTRA_ZEPHYR_MODULES'' replaces ''ZEPHYR_EXTRA_MODULES''