关于一个英语句子语法问题

此句是被动语态。
主语部分：people
谓语部分：are referred to (as)
宾语部分：white-collar workers

People主语
referred 谓语
"white-coller workers" 宾语
who work in offices定语（修饰主语）
are系动词

People 作主语
who work in offices 主语的定语（定语从句）
are referred to动词词组（被动语态）作谓语
white-coller workers宾语