[yocto] firmware image combining rootfs and kernel

[Karl Hiramoto]

Hi on my board, I build my  squashfs rootfs  and kernel image, and that 
works fine on yocto 9.0.1

How do i make my-image.bb   recipe,   build  a combined image? This 
would be similar to what openwrt does where you have a firmware.img   
that combines rootfs and kernel.
In openwrt there are different image file formats  for example: 
http://wiki.openwrt.org/doc/techref/header that contain  rootfs and kernel.

Does anyone know of any OE  recipies to handle this?  I need to have my 
own script build the firmware.img  that has dependencies of the 
virtual/kernel  and rootfs
And has variables that point  to  $DEPLOY_DIR / uImage  and $DEPLOY_DIR 
/ my-image.squashfs


Thanks,

karl