Toast coriander seeds in small skillet over medium heat until aromatic, stirring frequently, about 2 minutes. Cool slightly. Crush in mortar with pestle.
For relish: Char bell peppers over gas flame or under broiler until blackened on all sides. Enclose in paper bag 10 minutes. Peel and seed peppers; cut into 1/2-inch pieces. Set aside.
Heat 2 tablespoons oil in heavy large skillet over medium-high heat. Add corn and green onions and sauté until corn begins to brown in spots, about 5 minutes. Add garlic and thyme; sauté 2 minutes. Add wine and stir until liquid evaporates, about 1 minute. Remove from heat. Stir in bell peppers, lemon juice, honey, and remaining 2 tablespoons olive oil. Add 1 1/2 teaspoons crushed coriander seeds. (Relish can be made 8 hours ahead. Cover and refrigerate. Stir over medium heat until heated through before serving.) Stir parsley into relish. Season to taste with salt and pepper.
For salmon: Preheat oven to 400°F. Line large baking sheet with foil. Mix first 5 ingredients and remaining crushed coriander seeds in medium bowl. Brush salmon all over with mixture. Transfer to prepared baking sheet. Roast salmon until opaque in center, about 10 minutes. Transfer to platter. Spoon relish over salmon and serve.