docs: drop "Device tree support" section
We no longer provide any Linux kernel which do not have device-tree
support and all machines setup KERNEL_DEVICETREE correctly.
@@ -120,19 +120,6 @@ To build an initramfs image:
* Set the meta-rasberrypi variable (in raspberrypi.conf for example)
- `KERNEL_INITRAMFS = "-initramfs"`
-## Device tree support
-
-Device tree for RPi is only supported when using linux-raspberrypi 3.18+
-kernels.
-
-* Set `KERNEL_DEVICETREE` (in conf/machine/raspberrypi.conf)
- - the trailer is added to the kernel image before kernel install task. While
- creating the SDCard image, this modified kernel is put on boot partition (as
- kernel.img) as well as DeviceTree blobs (.dtb files).
-
-NOTE: `KERNEL_DEVICETREE` is default enabled for kernel >= 3.18 and always
-disabled for older kernel versions.
-
## Enable SPI bus
When using device tree kernels, set this variable to enable the SPI bus:
