Interviewing with Huawei / Qualcomm in Toronto. Will my AMD manager find out?

You have the right to interview with anyone

Not really, no one really cares unless the other side knows your manager

Hi, Are you on software side or hardware side?

No way. Small industry also means people don’t just tell others who they interview more so their competitors :)

Your manager won't find out unless someone told him. But why would your interviewing company do so?

The other side has the responsibility to keep your interview confidential unless you sign an agreement to allow them to reach out your current or previous employers ( normally being asked during background checking tho)