dft opt: Adding basic docs for the scan_opt command

Signed-off-by: Felipe Garay <fgaray@google.com>

Author: fgaray

src/dft/README.md

@@ -90,6 +90,19 @@ a result, this should be run after placement, and after `scan_replace`.
 execute_dft_plan
 ```
 
+### Scan Optimization
+
+**Note: This is currently not implement and this command currently operates as a
+nop**
+
+Performs scan optimizations on the design reordering the flops of the scan
+chains using the latest placement information.
+
+
+```tcl
+scan_opt
+```
+
 ## Example scripts
 
 This example will create scan chains with a max length of 10 bits mixing all the
@@ -114,6 +127,7 @@ Simply run the following script:
 ./test/regression
 ```
 
+
 ## Limitations
 
 * There are no optimizations for the scan chains. This is a WIP.