doc: build:kconfig:settings align with guidelines

configuration used for a particular build). By default, :file:`prj.conf` is

used.

1. If ``CONF_FILE`` is set, the configuration file(s) specified in it are

#. If ``CONF_FILE`` is set, the configuration file(s) specified in it are

   merged and used as the application configuration. ``CONF_FILE`` can be set

   in various ways:

   3. From the CMake variable cache

2. Otherwise if ``CONF_FILE`` is set, and a single configuration file of the

#. Otherwise if ``CONF_FILE`` is set, and a single configuration file of the

   form :file:`prj_<build>.conf` is used, then if file

   :file:`boards/<BOARD>_<build>.conf` exists in same folder as file

   :file:`prj_<build>.conf`, the result of merging :file:`prj_<build>.conf` and

   :file:`boards/<BOARD>_<build>.conf` is used.

3. Otherwise, :file:`prj_<BOARD>.conf` is used if it exists in the application

#. Otherwise, :file:`prj_<BOARD>.conf` is used if it exists in the application

   configuration directory.

4. Otherwise, if :file:`boards/<BOARD>.conf` exists in the application

#. Otherwise, if :file:`boards/<BOARD>.conf` exists in the application

   configuration directory, the result of merging it with :file:`prj.conf` is

   used.

5. Otherwise, if board revisions are used and

#. Otherwise, if board revisions are used and

   :file:`boards/<BOARD>_<revision>.conf` exists in the application

   configuration directory, the result of merging it with :file:`prj.conf` and

   :file:`boards/<BOARD>.conf` is used.

6. Otherwise, :file:`prj.conf` is used from the application configuration

#. Otherwise, :file:`prj.conf` is used from the application configuration

   directory. If it does not exist then a fatal error will be emitted.

All configuration files will be taken from the application's configuration