chore(doc): Restructure docs

Signed-off-by: Rahix <rahix@rahix.de>

Documentation/epicardium.rst → Documentation/epicardium/intro.rst

-Epicardium
-==========
+Epicardium Intro
+================
 
-Epicardium is the main firmware.  It runs on core0 and is based on FreeRTOS.
-Epicardium provides an API to a payload running on the other core which exposes
-most functionality.  This section of the docs details this "Epicardium API".
+Epicardium is the main component of the firmware.  It runs on core0 and is
+based on FreeRTOS.  Epicardium provides an API to a payload running on the
+other core which exposes most functionality.
 
 The API functions follow the kernel convention of either returning a boolean if
 the function is a predicate or returning a success integer (with negative
@@ -33,8 +33,3 @@ values denoting errors) if it is an action or imperative command.  To quote:
       for success or -EBUSY for failure.  In the same way, ``PCI device present`` is
       a predicate, and the pci_dev_present() function returns 1 if it succeeds in
       finding a matching device or 0 if it doesn't.
-
-.. toctree::
-   :maxdepth: 1
-
-   epicardium/api

Documentation/index.rst

@@ -12,7 +12,15 @@ The design roughly looks like this:
 
 .. toctree::
    :maxdepth: 2
-   :caption: Contents
+   :caption: Epicardium
 
-   epicardium
-   pycardium
+   epicardium/intro
+   epicardium/api
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Pycardium
+
+   pycardium/intro
+   pycardium/color
+   pycardium/leds

Documentation/pycardium.rst → Documentation/pycardium/intro.rst

-Pycardium
-=========
+Pycardium Intro
+===============
 
 Pycardium is a core1 payload based on MicroPython.  It can interface with
 card10 using the Epicardium API, which is wrapped in a bunch of python modules.
-These modules are documented in this section.
-
-.. toctree::
-   :maxdepth: 1
-   :caption: Modules:
-
-   pycardium/color
-   pycardium/leds