To return all interfaces of a device, you would issue a POST with this XML to the REST API endpoint '/spectrum/restful/models'. This is essentially a copy of the "Ports -> By Device IP" Locater search.
<?xml version="1.0" encoding="UTF-8"?>
<rs:model-request
xmlns:rs="http://www.ca.com/spectrum/restful/schema/request"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.ca.com/spectrum/restful/schema/request ../../../xsd/Request.xsd ">
<rs:target-models>
<rs:models-search>
<rs:search-criteria xmlns="http://www.ca.com/spectrum/restful/schema/filter">
<action-models>
<action-models>
<filtered-models>
<equals>
<model-type>SearchManager</model-type>
</equals>
</filtered-models>
<action>FIND_DEV_MODELS_BY_IP</action>
<attribute id="AttributeID.NETWORK_ADDRESS">
<value>x.x.x.x</value> <!-- Enter Device IP here -->
</attribute>
</action-models>
<action>GET_INTERFACES</action>
</action-models>
</rs:search-criteria>
</rs:models-search>
</rs:target-models>
<rs:requested-attribute id="0x1006e" />
<!-- Enter more attributes here -->
</rs:model-request>
Another nice easy endpoint to return only the interfaces with discovered connections, is to issue a GET to the REST API endpoint '/spectrum/restful/connectivity/<ip_address>'.