[spp] [PATCH] docs: update pri command

[ogawa.yasufumi@lab.ntt.co.jp]

From: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>

This patch is to add command examples for `launch` command added in
previous. It also adds an example of help message.

Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
---
 docs/guides/commands/primary.rst | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/docs/guides/commands/primary.rst b/docs/guides/commands/primary.rst
index 5032b37..687484d 100644
--- a/docs/guides/commands/primary.rst
+++ b/docs/guides/commands/primary.rst
@@ -6,6 +6,34 @@ Primary Commands
 
 Primary process is managed with ``pri`` command.
 
+``pri`` command takes a sub command. They must be separated with delimiter
+``;``. Some of sub commands take additional arguments.
+
+.. code-block:: console
+
+    spp > pri; SUB_CMD
+
+All of Sub commands are referred with ``help`` command.
+
+.. code-block:: console
+
+    spp > help pri
+    Send a command to primary process.
+
+        Show resources and statistics, or clear it.
+
+            spp > pri; status  # show status
+
+            spp > pri; clear   # clear statistics
+
+        Launch secondary process..
+
+            # Launch nfv:1
+            spp > pri; launch nfv 1 -l 1,2 -m 512 -- -n 1 -s 192.168....
+
+            # Launch vf:2
+            spp > pri; launch vf 2 -l 1,4-7 -m 512 -- --client-id 2 -s ...
+
 
 status
 ------
@@ -25,6 +53,7 @@ Show status fo spp_primary and forwarding statistics of each of ports.
         ID          rx          tx     rx_drop     rx_drop
          0           0           0           0           0
          1           0           0           0           0
+         ...
 
 
 clear
@@ -35,6 +64,7 @@ Clear statistics.
 .. code-block:: console
 
     spp > pri; clear
+    Clear port statistics.
 
 
 launch
-- 
2.7.4