some more docs, retore full Linux configs, wont touch that now

README.adoc

@@ -193,7 +193,24 @@ We tend to support the following Ubuntu host versions at least:
 
 ==== About the QEMU Buildroot setup
 
-link:https://en.wikipedia.org/wiki/Buildroot[] is a set of `make` scripts that downloads everything from source
+link:https://en.wikipedia.org/wiki/Buildroot[] is a set of `make` scripts that downloads from source and compiles compatible versions of:
+
+* GCC
+* Linux kernel
+* glibc
+* BusyBox
+
+It therefore produces a pristine, blob-less and debuggable setup.
+
+The price that you pay is that the first build takes a while, but it is well worth it.
+
+link:https://en.wikipedia.org/wiki/QEMU[QEMU] is a system simulator: it simulates a CPU and devices such as interrupt handlers, timers, UART, screen, keyboard, etc.
+
+QEMU is the leading cross arch system simulator as of 2018. It is even the default Android simulator that developers get with Android Studio 3 to develop apps without real hardware.
+
+QEMU is also supported by Buildroot in-tree, see e.g.: https://github.com/buildroot/buildroot/blob/2018.05/configs/qemu_aarch64_virt_defconfig
+
+All of this makes QEMU the natural choice of system simulator.
 
 === gem5 Buildroot setup
 
@@ -2574,9 +2591,9 @@ We also have one letter shorthand names for the architectures and `--arch` optio
 
 ....
 # aarch64
-./run --arch aarch64
+./run -a A
 # arm
-./run --arch arm
+./run -a a
 # x86_64
 ./run -a x
 ....
@@ -9665,10 +9682,10 @@ This directory has the following structure:
 
 Every directory inside it is a Buildroot package.
 
-Those packages get automatically added to Buildroot's `BR2_EXTERNAL` so you just need to turn them on during build, e.g.:
+Those packages get automatically added to Buildroot's `BR2_EXTERNAL`, so all you need to do is to turn them on during build, e.g.:
 
 ....
-BR2_SAMPLE_PACKAGE=y
+./build --buildroot-config BR2_SAMPLE_PACKAGE=y
 ....
 
 ==== patches