README: Whence cometh DTBs

Author: helehto

Diff for: README.md

@@ -9,6 +9,9 @@ To build (tested with Zig 0.9.0):
     $ zig build
 
 To run it in QEMU, you will need a compiled device tree (dtb) for the Raspberry
-Pi 3B+. Then, run it, supplying the device tree:
+Pi 3B+. One can be obtained from the Linux kernel source by running `make
+ARCH=arm dtbs` and having a look in `arch/arm/boot/dts`.
 
-    $ qemu-system-aarch64 -M raspi3b -kernel zig-out/bin/kernel8.img -dtb bcm2710-rpi-3-b.dtb
+Then, run it, supplying the device tree:
+
+    $ qemu-system-aarch64 -M raspi3b -kernel zig-out/bin/kernel8.img -dtb bcm2837-rpi-3-b-plus.dtb