From Armbian documentation (https://docs.armbian.com/User-Guide_Allwinner_overlays/)   Most in-circuit and GPIO based interfaces (SPI, I2C, I2S, …) don’t have a mechanism for detecting and identifying devices connected to the bus, so Linux kernel has to be told explicitly about the device and its configuration details.   While Device Tree is a way of describing hardware configuration to the kernel, Device Tree overlays are a way for modifying the DT in order to provide the ke