[bootlin/training-materials updates] master: slides/buildroot-advanced: add one slide about a few BR2_EXTERNAL trees (7234cf52)

[Thomas Petazzoni]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/7234cf520fe90fe2e32fab05a37f61339fd604b6

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commit 7234cf520fe90fe2e32fab05a37f61339fd604b6
Author: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
Date:   Fri Dec 10 21:57:23 2021 +0100

    slides/buildroot-advanced: add one slide about a few BR2_EXTERNAL trees
    
    Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>


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7234cf520fe90fe2e32fab05a37f61339fd604b6
 slides/buildroot-advanced/buildroot-advanced.tex | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/slides/buildroot-advanced/buildroot-advanced.tex b/slides/buildroot-advanced/buildroot-advanced.tex
index 7659e2c5..521dcb39 100644
--- a/slides/buildroot-advanced/buildroot-advanced.tex
+++ b/slides/buildroot-advanced/buildroot-advanced.tex
@@ -218,6 +218,27 @@ BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="$(BR2_EXTERNAL_<NAME>_PATH)/board/<company>
 
 \end{frame}
 
+\begin{frame}{Examples of {\tt BR2\_EXTERNAL} trees}
+  \begin{itemize}
+  \item There are a number of publicly available {\tt BR2\_EXTERNAL}
+    trees, especially from hardware vendors:
+    \begin{itemize}
+    \item \code{buildroot-external-st}, maintained by Bootlin in
+      partnership with ST, containing example configurations for the
+      STM32MP1 platforms.\\
+      \url{https://github.com/bootlin/buildroot-external-st}
+    \item \code{buildroot-external-microchip}, containing example
+      configurations, additional packages and demo applications for
+      Microchip ARM platforms.\\
+      \url{https://github.com/linux4sam/buildroot-external-microchip}
+    \item \code{buildroot-external-boundary}, containing example
+      configurations for Boundary Devices boards, mainly based on NXP
+      i.MX processors.\\
+      \url{https://github.com/boundarydevices/buildroot-external-boundary}
+    \end{itemize}
+  \end{itemize}
+\end{frame}
+
 \begin{frame}{Package-specific targets: basics}
   \begin{itemize}
   \item Internally, each package is implemented through a number of