[chef] improvements to chef readme file (#20316)

* chg: improvements to chef readme file

* chg: restyle

Change-Id: I9dce3fd2d94df0080ca710a89f94c45bfb013ea5

examples/chef/README.md

@@ -1,25 +1,23 @@
 # MATTER CHEF APP
 
-The purpose of the chef app is to to increase the coverage of device types in
-Matter.
+The purpose of the chef app is to to:
 
-It uses the shell app a starting point, adding the processing of ZAP files and
-the support of a few targets under a unified build script: `chef.py`.
+1. Increase the coverage of device types in Matter
+2. Provide a sample application that may have its data model easily configured.
+
+Chef uses the shell app a starting point, but processes the data model defined
+on ZAP files during build time. This procedure is handled by its unified build
+script: `chef.py`.
 
 As it incorporates the processing of ZAP files as part of the build process, it
 does not use `zzz_generated`, but rather places the auto-generated zap artifacts
-under its `zap-generated` temporary folder.
-
-All device types available (DM/IM .zap files) are found inside the `devices`
-folder.
+under its `out` temporary folder.
 
-## Building a Sample Application
-
-Run `chef.py -h` to see the available commands
+All device types available (.zap files) are found inside the `devices` folder.
 
 ## Building your first sample
 
-1. Make sure you have the toolchain installed for your desired target
+1. Make sure you have the toolchain installed for your desired target.
 2. Run `chef.py` the first time to create a `config.yaml` configuration file. If
    you already have SDK environment variables such as IDF_PATH (esp32) and
    ZEPHYR_BASE (nrfconnect) it will use those values as default.
@@ -44,11 +42,12 @@ Run `chef.py -h` to see the available commands
     TTY: /dev/ttyUSB0
 ```
 
-4. Run `$ chef.py -u` to update zap and the toolchain (on selected platforms)
+4. Run `$ chef.py -u` to update zap and the toolchain (on selected platforms).
 5. Run `$ chef.py -gzbf -t <platform> -d lighting`. This command will run the
    ZAP GUI opening the `devices/lighting.zap` file and will allow editing. It
    will then generate the zap artifacts, place them on the `zap-generated`
-   folder, run a build and flash the binary in your target
+   folder, run a build and flash the binary in your target.
+6. Run `chef.py -h` to see all available commands.
 
 ## Creating a new device type in your device library
 
@@ -59,6 +58,27 @@ Run `chef.py -h` to see the available commands
    into the `devices` folder. This device is now available for the script. See
    `chef.py -h` for a list of devices available.
 
+## Folder Structure and Guidelines
+
+-   `<platform>`: build system and `main.cpp` file for every supported platform.
+    When porting a new platform, please minimize the source code in this folder,
+    favoring the `common` folder for code that is not platform related.
+-   `common`: contains code shared between different platforms. It may contain
+    source code that enables specific features such as `LightingManager` class
+    or `LockManager`, as long as the application dynamically identify the
+    presence of the relevant cluster configurations and it doesn't break the use
+    cases where chef is built without these clusters.
+-   `devices`: contains the data models that may be used with chef. As of Matter
+    1.0 the data models are defined using .zap files.
+-   `out`: temporary folder used for placing ZAP generated artifacts.
+-   `sample_app_util`: guidelines and scripts for generating file names for new
+    device types committed to the `devices` folder.
+-   `config.yaml`: contains general configuration for the `chef.py` script. As
+    of Matter 1.0 this is used exclusively for toolchain and TTY interface
+    paths.
+-   `chef.py`: main script for generating samples. More info on its help
+    `chef.py -h`.
+
 ## CI
 
 All CI jobs for chef can be found in `.github/workflows/chef.yaml`.