doc: use graphviz for intro boot-flow diagram

Trying out the graphviz capability rather than using static images that
we can't easily modify.  Also updated the site logo that was too wide.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>

doc/conf.py

@@ -32,7 +32,11 @@
 # ones.
 extensions = ['breathe', 'sphinx.ext.graphviz']
 
-graphviz_output_format='svg'
+graphviz_output_format='png'
+graphviz_dot_args=[
+   '-Nfontname="verdana"',
+   '-Gfontname="verdana"',
+   '-Efontname="verdana"']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -174,7 +178,7 @@
 #
 # html_theme_options = {}
 
-html_logo = 'images/ACRN_Logo_300w.png'
+html_logo = 'images/ACRN_Logo_200w.png'
 html_favicon = 'images/ACRN-favicon-32x32.png'
 
 numfig = True

doc/introduction/images/boot-flow.dot

@@ -0,0 +1,6 @@
+digraph G {
+   rankdir=LR;
+   bgcolor="transparent";
+   UEFI -> "acrn.efi" -> "OS\nBootloader" ->
+     "SOS\nKernel" -> "ACRN\nDevice Model" -> "Virtual\nBootloader";
+}

doc/introduction/index.rst

@@ -140,11 +140,10 @@ Boot Sequence
 In :numref:`boot-flow` we show a verified Boot Sequence with UEFI
 on an Intel |reg| Architecture platform NUC (see :ref:`hardware`).
 
-.. figure:: images/boot-flow.png
-   :align: center
+.. graphviz:: images/boot-flow.dot
    :name: boot-flow
-
-   ACRN Hypervisor Boot Flow
+   :align: center
+   :caption: ACRN Hypervisor Boot Flow
 
 The Boot process proceeds as follows: