README: Add score comparison instructions

Signed-off-by: Pawel Langowski <pawel.langowski@3mdeb.com>

README.md

@@ -24,7 +24,7 @@ but also many more coreboot distributions like heads.
 ## Usage
 
 ```bash
-usage: openness_score.py [-o OUTPUT] [-v] [-V] [file]
+usage: openness_score.py [-c proprietary_file] [-p PLATFORM] [-o OUTPUT] [-v] [-m [-V] [file]
 
 Calculate Dasharo Openness Score for firmware images
 
@@ -32,6 +32,10 @@ positional arguments:
   file                  Firmware binary file to be parsed
 
 options:
+  -c proprietary_file, --compare proprietary_file
+                        Compare Dasharo and proprietary firmware scores and store result in a Markdown table. file should be the Dasharo binary and proprietary_file should  be the proprietary firmware binary.
+  -p PLATFORM, --platform PLATFORM
+                        Platform model to provide to the table when --compare is set.
   -o OUTPUT, --output OUTPUT
                         Specifies the directory where to store the results
   -a MICROARCH, --microarch MICROARCH
@@ -75,6 +79,33 @@ The utility will produce 3 files:
   precise numbers and detailed classification of firmware image components
   to closed-source, open-source, data and empty categories
 
+Example with `--compare` flag:
+
+```bash
+./openness_score/openness_score.py msi_ms7d25_v1.1.4_ddr4.rom -c E7D25IMS.1M1 -p "MS-7D25"
+```
+
+Aside from the 3 files mentioned above, this will also produce `compare.md` - A
+Markdown table containing the score comparison between the two binaries. If the
+file already exists, the result will be appended as a single row.
+
+The table contains the following metrics:
+
+- `closed-source diff`
+- `data size diff`
+- `empty space diff`
+
+Each metric is calculated using the formula:
+
+```txt
+(Dasharo <type> size - Proprietary <type> size) * 100 / Proprietary <type> size
+```
+
+`<type>` is replaced by `closed-source`, `data` or `empty space` accordingly.
+
+You can use `scripts/compare.sh` to generate a comparison table for common
+Dasharo platforms. For more information, see the script's help.
+
 **The utility currently supports coreboot and pure UEFI images only.**
 
 ### Examples