As mentioned before, problems with the syntax of device tree files usually result in the kernel crashing early in the boot process. Other types of problems are more subtle and usually appear once a driver is making use of the information provided by the device tree. For both types of problems, it is helpful to be able to look not only at the device tree syntax file, but also at the device tree blob, as it is read by both U-Boot and the Linux kernel. It may also be helpful to modify the device tree on the fly using the tools that U-Boot offers.
Let's see how to access the device tree at runtime, both from a running U-Boot and Linux.