How to pass command line arguments via the device tree

Need to append kernel boot arguments that are provided within the kernel image

Why would this be needed?

u-boot can pass device tree, boot arguments for the Linux kernel, load the Linux image from a sdcard or flash chip via the boot script.  Very flexible and powerful idea.  But, if changes need to be done of enhancing the kernel arguments due to some new feature, then u-boot environment needs change.  

To simplify this process, the kernel can provide a default boot arguments, so, if a kernel feature or some feature then the can be added.  But here is the issue, if the device tree is appended image then the boot arguments need to come from the device tree not the compiled in aurgments. 

For example:

chosen {
  bootargs = "console=ttyS0,115200 loglevel=8";
  
 }