docs: user guides

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

docs/guides/cni-networking.md

@@ -0,0 +1,23 @@
+# CNI networking
+
+It can be useful to use a bridge network for your builder if for example you
+encounter a network port contention during multiple builds. If you're using
+the BuildKit image, CNI is not yet available in it, but you can create
+[a custom BuildKit image with CNI support](https://github.com/moby/buildkit/blob/master/docs/cni-networking.md).
+
+Now build this image:
+
+```console
+$ docker buildx build --tag buildkit-cni:local --load .
+```
+
+Then [create a `docker-container` builder](../reference/buildx_create.md) that
+will use this image:
+
+```console
+$ docker buildx create --use \
+  --name mybuilder \
+  --driver docker-container \
+  --driver-opt "image=buildkit-cni:local" \
+  --buildkitd-flags "--oci-worker-net=cni"
+```