If you have two or more MS-A2 in a master/slave config you can address the system as well as the individual state:
…
state_topic: "homeassistant/sensor/MSA-2xxNUMMER_MASTER/quick/state"
value_template: "{{ value_json.sys_soc }}"
…
state_topic: "homeassistant/sensor/MSA-2xxNUMMER_MASTER/quick/state"
value_template: "{{ value_json.soc }}"
state_topic: "homeassistant/sensor/MSA-2xxNUMMER_SLAVE/quick/state"
value_template: "{{ value_json.soc }}"