Interesting question. In my view, MARKETING STRATEGY is one type of functional strategy. Other functional strategies include: HRM strategy, Supply Chain strategy, Financial strategy, Sales strategy, etc. Typically, in large firms, after the business strategy is formulated, the various functions in the firm create their functional strategy to align with the business strategy.
More problematic is the term STRATEGIC MARKETING. This term can best be understood when it is compared with operational marketing, which is about such things as advertising, organising events, PR, customer databases, etc. Strategic Marketing on the other hand is dealing with such things as: product (line) strategy, corporate reputation, branding, strategic planning, etc.