Merge pull request #1241 from jedevc/docker-driver-docs

docs: add minimal docker driver docs

docs/guides/drivers/docker.md

@@ -0,0 +1,50 @@
+# Docker driver
+
+The buildx docker driver is the default builtin driver, that uses the BuildKit
+server components built directly into the docker engine.
+
+No setup should be required for the docker driver - it should already be
+configured for you:
+
+```console
+$ docker buildx ls
+NAME/NODE       DRIVER/ENDPOINT      STATUS   BUILDKIT PLATFORMS
+default         docker                                 
+  default       default              running  20.10.17 linux/amd64, linux/386
+```
+
+This builder is ready to build with out-of-the-box, requiring no extra setup,
+so you can get going with a `docker buildx build` as soon as you like.
+
+Depending on your personal setup, you may find multiple builders in your list
+the use the docker driver. For example, on a system that runs both a package
+managed version of dockerd, as well as Docker Desktop, you might have the
+following:
+
+```console
+NAME/NODE       DRIVER/ENDPOINT STATUS  BUILDKIT PLATFORMS
+default         docker                           
+  default       default         running 20.10.17 linux/amd64, linux/386
+desktop-linux * docker                           
+  desktop-linux desktop-linux   running 20.10.17 linux/amd64, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/arm/v7, linux/arm/v6
+```
+
+This is because the docker driver builders are automatically pulled from
+the available [Docker Contexts](https://docs.docker.com/engine/context/working-with-contexts/).
+When you add new contexts using `docker context create`, these will appear in
+your list of buildx builders.
+
+Unlike the [other drivers](../index.md), builders using the docker driver
+cannot be manually created, and can only be automatically created from the
+docker context. Additionally, they cannot be configured to a specific BuildKit
+version, and cannot take any extra parameters, as these are both preset by the
+Docker engine internally.
+
+If you want the extra configuration and flexibility without too much more
+overhead, then see the help page for the [docker-container driver](./docker-container.md).
+
+## Further reading
+
+For more information on the docker driver, see the [buildx reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver).
+
+<!--- FIXME: for 0.9, make reference link relative --->

docs/guides/drivers/index.md

@@ -8,7 +8,7 @@ Currently, we support the following drivers:
 
 - The `docker` driver, that uses the BuildKit library bundled into the Docker
   daemon.
-  ([reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver))
+  ([guide](./docker.md), [reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver))
 - The `docker-container` driver, that launches a dedicated BuildKit container
   using Docker, for access to advanced features.
   ([guide](./docker-container.md), [reference](https://docs.docker.com/engine/reference/commandline/buildx_create/#driver))