doc: Add a description for bootmeth_pxe

Add documentation for the pxe bootmeth.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
diff --git a/doc/develop/bootstd/overview.rst b/doc/develop/bootstd/overview.rst
index 26b7985..6afa1c2 100644
--- a/doc/develop/bootstd/overview.rst
+++ b/doc/develop/bootstd/overview.rst
@@ -417,7 +417,7 @@
 Bootmeth drivers are provided for booting from various media:
 
    - :doc:`extlinux / syslinux <extlinux>` boot from a storage device
-   - extlinux boot from a network (PXE)
+   - :doc:`extlinux / syslinux <extlinux>` boot from a network (PXE)
    - U-Boot scripts from disk, network or SPI flash
    - EFI boot using bootefi from disk
    - VBE