doc: terminology cleanup in file names, labels

- Replace SOS with Service VM
- Replace UOS with User VM

Signed-off-by: Amy Reyes <amy.reyes@intel.com>

doc/developer-guides/hld/hld-security.rst

@@ -254,7 +254,7 @@ In ACRN, User VM Secure Boot can be enabled as follows:
 #. Sign the User VM images with `db.key` and `db.crt`.
 #. Boot the User VM with Secure Boot enabled.
 
-.. _sos_hardening:
+.. _service_vm_hardening:
 
 Service VM Hardening
 --------------------
@@ -732,7 +732,7 @@ must be disabled in a production release. Users who want to use this
 feature must possess the private signing key to re-sign the image after
 enabling the configuration.
 
-.. _uos_suspend_resume:
+.. _user_vm_suspend_resume:
 
 User VM Suspend/Resume
 ~~~~~~~~~~~~~~~~~~~~~~
@@ -1041,7 +1041,7 @@ Note that there are some security considerations in this design:
 
 Keeping the Service VM system as secure as possible is a very important goal in
 the system security design. Follow the recommendations in
-:ref:`sos_hardening`.
+:ref:`service_vm_hardening`.
 
 SEED Derivation
 ---------------
@@ -1065,7 +1065,7 @@ the restore state hypercall is called only by vBIOS when the User VM is ready to
 resume from suspend state.
 
 For security design considerations of handling secure world S3,
-read the previous section: :ref:`uos_suspend_resume`.
+read the previous section: :ref:`user_vm_suspend_resume`.
 
 Platform Security Feature Virtualization and Enablement
 =======================================================

doc/developer-guides/hld/virtio-net.rst

@@ -414,7 +414,7 @@ prepared in the Service VM before we start. We need to create a bridge and at
 least one TAP device (two TAP devices are needed to create a dual
 virtual NIC) and attach a physical NIC and TAP device to the bridge.
 
-.. figure:: images/network-virt-sos-infrastruct.png
+.. figure:: images/network-virt-service-vm-infrastruct.png
    :align: center
    :width: 900px
    :name: net-virt-infra