This is the device tree overlay(s) and its make.

The purpose of the overlay is to define the system
for the mts-io driver and/or mtac drivers.

The correct overlay for the system is loaded at
runtime before loading the mts-io driver.  A method
for doing this is the device tree configfs driver.

See this for the format of an overlay:

https://www.kernel.org/doc/Documentation/devicetree/overlay-notes.txt

The biggest flaw in overlays, is the inablitiy to use
the phandle described in an alias in the boot
time device tree in an overlay, so it appears
to be impossible to reference nodes in the main
device tree in any shorthand method.  For instance, it
is common to reference a "pio" in device tree to
use a PIO with GPIO.  For example, it does not appear
to be possible to use &pioC in the overlay without
redefining it.

The recipe that uses the overlay reads a comment
in the overlay source to determine the destination
and any symlink locations.

The comment in the file must be as follows for
locations and symlinks:

/*
 * Put:     /a/b/c/d.dtbo
 * Link:    /a/x/y/d.dtbo
 *
 */

The install is looking for a line that
starts with " * Put:  " or " * Link: ".
Extra spaces before the path are allowed.
The link will always point at the path
specified by Put.

The path given is relative to the device
tree overlay location.