docs: user guides

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

docs/guides/custom-network.md

@@ -0,0 +1,48 @@
+# Using a custom network
+
+[Create a network](https://docs.docker.com/engine/reference/commandline/network_create/)
+named `foonet`:
+
+```console
+$ docker network create foonet
+```
+
+[Create a `docker-container` builder](../reference/buildx_create.md) named
+`mybuilder` that will use this network:
+
+```console
+$ docker buildx create --use \
+  --name mybuilder \
+  --driver docker-container \
+  --driver-opt "network=foonet"
+```
+
+Boot and [inspect `mybuilder`](../reference/buildx_inspect.md):
+
+```console
+$ docker buildx inspect --bootstrap
+```
+
+[Inspect the builder container](https://docs.docker.com/engine/reference/commandline/inspect/)
+and see what network is being used:
+
+```console
+$ docker inspect buildx_buildkit_mybuilder0 --format={{.NetworkSettings.Networks}}
+map[foonet:0xc00018c0c0]
+```
+
+## What's `buildx_buildkit_mybuilder0`?
+
+`buildx_buildkit_mybuilder0` is the container name. It can be broken down like this:
+
+* `buildx_buildkit_` is a hardcoded prefix
+* `mybuilder0` is the name of the node (defaults to builder name + position in the list of nodes)
+
+```console
+$ docker buildx ls
+NAME/NODE     DRIVER/ENDPOINT                        STATUS                 PLATFORMS
+mybuilder *   docker-container
+  mybuilder0  unix:///var/run/docker.sock            running                linux/amd64, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6     
+default       docker
+  default     default                                running                linux/amd64, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/arm/v7, linux/arm/v6
+```