docs: update README for SC598 bootstrap image

Signed-off-by: Ozan Durgut <ozan.durgut@analog.com>

Author: ozan956

readme.md

@@ -1,26 +1,56 @@
 # ADI br2-external
 
 This [br2-external](https://buildroot.org/downloads/manual/manual.html#outside-br-custom)
-contains Buildroot configuration specific to ADI that can not be mainlined.
-Generic support for ADI evaluation boards is implemented in the [ADI Buildroot
-tree](github.com/analogdevicesinc/buildroot).
+contains Buildroot configuration specific to ADI that cannot be mainlined.
+Generic support for ADI evaluation boards is implemented in the
+[ADI Buildroot tree](github.com/analogdevicesinc/buildroot).
 
-```
+## Getting Started
+
+```sh
 git clone --recurse-submodules https://github.com/analogdevicesinc/br2-external.git
 cd br2-external/buildroot
 make BR2_EXTERNAL="${PWD}/.." adi_sc598_ezkit_defconfig
+```
+
+Additional configuration is applied using Buildroot fragments:
+
+```sh
 support/kconfig/merge_config.sh .config \
     ../configs/buildroot.fragment \
-    ../configs/debug.fragment
+    <ADI Configuration fragments>
 ```
 
-Then follow the board specific instructions in `buildroot/board/adi/`.
-
-## ADI configuration
+## ADI Configuration Fragments
 
 - `configs/buildroot.fragment`
     - Configure Buildroot to speed up builds
 - `configs/debug.fragment`
     - Enable debugging in U-Boot and the kernel
     - Build the kernel image with an embedded root filesystem to reduce
       complexity around writing and mounting a root filesystem from storage
+- `configs/bootstrap.fragment`  
+    - Enable a minimal bootstrap / installer image.  
+    - Includes only the tools required to program boot media.
+
+## Example Builds
+
+### Debug Image
+
+```sh
+make BR2_EXTERNAL="${PWD}/.." adi_sc598_ezkit_defconfig
+support/kconfig/merge_config.sh .config \
+    ../configs/buildroot.fragment \
+    ../configs/debug.fragment
+make -j$(nproc)
+```
+
+### Bootstrap Image
+
+```sh
+make BR2_EXTERNAL="${PWD}/.." adi_sc598_ezkit_defconfig
+support/kconfig/merge_config.sh .config \
+    ../configs/buildroot.fragment \
+    ../configs/bootstrap.fragment
+make -j$(nproc)
+```