docs: add architecture outline (#341)

Signed-off-by: Panos Vagenas <35837085+vagenas@users.noreply.github.com>

docs/concepts/architecture.md

@@ -0,0 +1,19 @@
+![docling_architecture](../assets/docling_arch.png)
+
+In a nutshell, Docling's architecture is outlined in the diagram above.
+
+For each document format, the *document converter* knows which format-specific *backend* to employ for parsing the document and which *pipeline* to use for orchestrating the execution, along with any relevant *options*.
+
+!!! tip
+
+    While the document converter holds a default mapping, this configuration is parametrizable, so e.g. for the PDF format, different backends and different pipeline options can be used — see [Usage](../usage.md#adjust-pipeline-features).
+
+The *conversion result* contains the [*Docling document*](./docling_document.md), Docling's fundamental document representation.
+
+Some typical scenarios for using a Docling document include directly calling its *export methods*, such as for markdown, dictionary etc., or having it chunked by a *chunker*.
+
+For more details on Docling's architecture, check out the [Docling Technical Report](https://arxiv.org/abs/2408.09869).
+
+!!! note
+
+    The components illustrated with dashed outline indicate base classes that can be subclassed for specialized implementations.

docs/concepts/index.md

@@ -1,3 +1 @@
-In this area you can find guides on the main Docling concepts.
-
-Use the navigation on the left to browse through them.
+Use the navigation on the left to browse some core Docling concepts.

docs/examples/index.md

@@ -1,3 +1 @@
-In this area you can find examples covering a range of possible workflows and use cases.
-
-Use the navigation on the left to browse through them.
+Use the navigation on the left to browse through examples covering a range of possible workflows and use cases.

docs/integrations/index.md

@@ -1,3 +1 @@
-In this area you can find guides on the Docling integrations with popular frameworks and tools.
-
-Use the navigation on the left to browse through them.
+Use the navigation on the left to browse through Docling integrations with popular frameworks and tools.

mkdocs.yml

@@ -58,6 +58,7 @@ nav:
     - Docling v2: v2.md
   - Concepts:
     - Concepts: concepts/index.md
+    - Architecture: concepts/architecture.md
     - Docling Document: concepts/docling_document.md
   #   - Chunking: concepts/chunking.md
   - Examples: