Linux kernel configuration: Pin Muxin and Device Tree
After the initialization, you have to start Linux. To do this, you have to describe the card you want it to support. This happens in two main steps:
1. The pin muxing which consists in configuring each of the processor contacts in relation to the tracks of your card.
2. Then, writing the device-tree gives the kernel the correspondence between the buses and the components of the card with drivers
At the end of this phase (also called bring-up) the kernel is able to use the hardware to boot, read, write, communicate and run
embedded software.