doc: Add three new glossaries

Add three new glossaries: "Hybrid Mode", "Partition Mode", "Sharing Mode".

Signed-off-by: lirui34 <ruix.li@intel.com>

Author: lirui34

doc/glossary.rst

@@ -86,6 +86,11 @@ Glossary of Terms
    High GM
       See :term:`Hidden GM`
 
+   Hybrid Mode
+      One of three operation modes (hybrid, partition, sharing) that ACRN supports.
+      In this mixed mode, physical hardware resources can be both partitioned to
+      individual user VMs and shared across user VMs.
+
    I2C
       Inter-Integrated Circuit
 
@@ -124,6 +129,10 @@ Glossary of Terms
       the Project ACRN architecture, pass-through devices are owned by the
       foreground OS.
 
+   Partition Mode
+      One of three operation modes (partition, sharing, hybrid) that ACRN supports.
+      Physical hardware resources are partitioned to individual user VMs.
+
    PCI
       Peripheral Component Interface.
 
@@ -180,6 +189,10 @@ Glossary of Terms
       access hardware resources directly by running native drivers and
       provides device sharing services to User VMs via the Device Model.
 
+   Sharing Mode
+      One of three operation modes (sharing, hybrid, partition) that ACRN supports.
+      Most of the physical hardware resources are shared across user VMs.
+
    SOS
       Obsolete, see :term:`Service VM`