[PATCH v3 4/4] doc: add an example arm64 cross file

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

The docs mention modifications and additions to the cross file, but
there is no demonstration of how those should look like.

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
Acked-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 .../linux_gsg/cross_build_dpdk_for_arm64.rst  | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
index 045cc05c65..f491725948 100644
--- a/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
+++ b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
@@ -137,6 +137,32 @@ Cross Compiling DPDK with GNU toolchain using Meson
    ones, which have an extra "-none-" in their name. Please modify the cross
    file binaries accordingly when using the downloaded cross compilers.
 
+   An example cross file with modified names and added numa paths would look
+   like this:
+
+   .. code-block:: console
+
+      [binaries]
+      c = 'aarch64-none-linux-gnu-gcc'
+      cpp = 'aarch64-none-linux-gnu-cpp'
+      ar = 'aarch64-none-linux-gnu-gcc-ar'
+      strip = 'aarch64-none-linux-gnu-strip'
+      pkgconfig = 'aarch64-linux-gnu-pkg-config' # the downloaded binaries
+         # don't contain a pkgconfig binary, so it's not modified
+      pcap-config = ''
+
+      [host_machine]
+      system = 'linux'
+      cpu_family = 'aarch64'
+      cpu = 'armv8-a'
+      endian = 'little'
+
+      [properties]
+      # Generate binaries that are portable across all Armv8 machines
+      platform = 'generic'
+      c_args = ['-I<numa_install_dir>/include']  # replace <numa_install_dir>
+      c_link_args = ['-L<numa_install_dir>/lib'] # with your path
+
 To cross-compile DPDK on a desired target machine we can use the following
 command::
 
-- 
2.20.1