PCI: mediatek: Switch to use platform_get_resource_byname()

This is a transitional patch.  We currently use platfarm_get_resource() for
retrieving the IOMEM resources, but there might be some chips don't have
subsys/shared registers part, which depends on platform design, and these
will be introduced in further patches.

Switch this function to use the platform_get_resource_byname() so that the
binding can be agnostic of the resource order.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/host/pcie-mediatek.c

@@ -295,7 +295,8 @@ static int mtk_pcie_parse_port(struct mtk_pcie *pcie,
 		return err;
 	}
 
-	regs = platform_get_resource(pdev, IORESOURCE_MEM, slot + 1);
+	snprintf(name, sizeof(name), "port%d", slot);
+	regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
 	port->base = devm_ioremap_resource(dev, regs);
 	if (IS_ERR(port->base)) {
 		dev_err(dev, "failed to map port%d base\n", slot);
@@ -336,13 +337,15 @@ static int mtk_pcie_subsys_powerup(struct mtk_pcie *pcie)
 	struct resource *regs;
 	int err;
 
-	/* get shared registers */
-	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	/* get shared registers, which are optional */
+	regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "subsys");
+	if (regs) {
 		pcie->base = devm_ioremap_resource(dev, regs);
 		if (IS_ERR(pcie->base)) {
 			dev_err(dev, "failed to map shared register\n");
 			return PTR_ERR(pcie->base);
 		}
+	}
 
 	pcie->free_ck = devm_clk_get(dev, "free_ck");
 	if (IS_ERR(pcie->free_ck)) {