docs: Include instructions on enable Remoteproc Runtime in userspace

docs/PERMISSION_SETTING.md

@@ -0,0 +1,50 @@
+# Permission setting for non-root users' usage of Remoteproc Runtime
+
+For non-root users to use Remoteproc Runtime, the remoteproc driver and the container engine must be accessible for this user.
+
+## How to set Remoteproc Runtime to be accessible by non-root users
+
+### 1. Make remoteproc driver accessible to the user
+
+Usually, remoteproc driver can only be accessible to root. To change this setting, follow the below instructions:
+
+1. Create a group and add your user:
+
+   ```sh
+   sudo groupadd remoteproc
+   sudo usermod -aG remoteproc "$USER"
+   ```
+
+   Log out and log back in to refresh group membership
+
+2. Use systemd-tmpfiles to set mode/owner on every boot (and re-apply easily):
+
+   Create /etc/tmpfiles.d/remoteproc.conf with following:
+
+   ```
+   f /sys/class/remoteproc/remoteproc0/state                0664  root remoteproc -   -
+   f /sys/class/remoteproc/remoteproc0/firmware             0664  root remoteproc -   -
+   f /sys/class/remoteproc/remoteproc0/name                 0664  root remoteproc -   -
+   ```
+
+   Add similar lines for each additional remoteproc device (e.g., remoteproc1, remoteproc2, etc.) as needed.
+
+3. Apply the change in remoteproc.conf using root permission. This needs to be done on each boot.:
+   ```sh
+   sudo systemd-tmpfiles --create /etc/tmpfiles.d/remoteproc.conf
+   ```
+4. Log in as a user in the remoteproc group and try the following commands to make sure that you can access the remoteproc driver as this user:
+   ```sh
+   # read state
+   cat /sys/class/remoteproc/remoteproc0/state
+   # start/stop
+   echo start | tee /sys/class/remoteproc/remoteproc0/state
+   echo stop  | tee /sys/class/remoteproc/remoteproc0/state
+   ```
+
+### 2. Set the firmware path to somewhere accessible by the user
+
+1. Ensure that the path of the folder that contains your firmware is written to `/sys/module/firmware_class/parameters/path`. You need root permission for this.
+   ```sh
+   sudo echo <your firmware folder path> > /sys/module/firmware_class/parameters/path
+   ```

docs/USAGE.md

@@ -48,6 +48,10 @@ Remoteproc Runtime supports several container engines, but the specifics of inte
 - **[Container Runtime (Podman)](#container-runtime-podman)** - For Podman deployments
 - **[Container Runtime (standalone)](#container-runtime-standalone)** - For direct OCI runtime usage
 
+Because the driver interfaces are located in the `/sys/class` directory, controlling remoteproc devices requires elevated permissions.
+
+To ensure Remoteproc Runtime has the necessary privileges, either run your container engine (e.g., Docker daemon, K3S, or Podman) with root privileges, or follow the [permission setting instructions](./PERMISSION_SETTING.md).
+
 ### Containerd Shim (Docker, K3s, etc)
 
 1. **Install the shim and runtime**