[docs] Add design intro section.

Signed-off-by: Miguel Osorio <miguelosorio@google.com>

Author: moidx

docs/src/design/README.md

@@ -1 +1,17 @@
-# Design
+# Design
+
+This section contains design documents that provide a detailed overview of the
+design and implementation of the OpenProt project. These documents are intended
+to provide guidance to developers and anyone interested in the internal workings
+of the project.
+
+## Documents
+
+-   [**Generic Digest Server Design Document**](./driver-hubris-hash.md): This
+    document describes the design and architecture of a generic digest server
+    for Hubris OS that supports both SPDM and PLDM protocol implementations.
+
+-   [**Converting Rust HAL Traits to Idol Interfaces**](./rust-trait-to-idl-conversion.md):
+    A practical guide that explains how to transform Rust Hardware Abstraction
+    Layer (HAL) traits into Idol interface definitions for use in Hubris-based
+    systems.