Index: sys/dev/fdt/simplebus.h
===================================================================
--- sys/dev/fdt/simplebus.h
+++ sys/dev/fdt/simplebus.h
@@ -61,4 +61,6 @@
     const char *name, int unit, struct simplebus_devinfo *di);
 struct simplebus_devinfo *simplebus_setup_dinfo(device_t dev, phandle_t node,
     struct simplebus_devinfo *di);
+int simplebus_get_base_addr(phandle_t node, u_long start, u_long size,
+    u_long *phys_addr);
 #endif	/* _FDT_SIMPLEBUS_H */
Index: sys/dev/fdt/simplebus.c
===================================================================
--- sys/dev/fdt/simplebus.c
+++ sys/dev/fdt/simplebus.c
@@ -39,6 +39,7 @@
 #include <dev/ofw/ofw_bus_subr.h>
 
 #include <dev/fdt/simplebus.h>
+#include <dev/fdt/fdt_common.h>
 
 /*
  * Bus interface.
@@ -421,3 +422,108 @@
 	rv += bus_print_child_footer(bus, child);
 	return (rv);
 }
+
+/* Limit size of stack buffers */
+#define MAX_RANGES 8
+#define MAX_CELLS_PER_RANGE 6
+
+/* Calculate absolute physical base address of a device node */
+int
+simplebus_get_base_addr(phandle_t node, u_long start, u_long size,
+    u_long *phys_addr)
+{
+	struct simplebus_range ranges[MAX_RANGES];
+	cell_t base_ranges[MAX_CELLS_PER_RANGE * MAX_RANGES];
+	ssize_t nbase_ranges, rv;
+	int i, j, k, nranges;
+	pcell_t addr_cells, host_address_cells, size_cells;
+	u_long end;
+
+	end = start + size - 1;
+	/* Get parent bus of the node */
+	node = OF_parent(node);
+
+	/* Work from the immediate parent of the device node up to the root node
+	 * translating the base address through 'ranges' properties of every
+	 * simple-bus parent, the same way simplebus_alloc_resource() does it.
+	 */
+	for (; node != 0; node = OF_parent(node)) {
+		if (!fdt_is_compatible(node, "simple-bus"))
+			continue;
+
+		rv = OF_getencprop(node, "#address-cells", &addr_cells,
+		    sizeof(addr_cells));
+		if (rv <= 0)
+			addr_cells = 2; /* Default size used by simplebus */
+
+		rv = OF_getencprop(OF_parent(node), "#address-cells",
+		    &host_address_cells, sizeof(host_address_cells));
+		if (rv <= 0)
+			host_address_cells = 2; /* Default size */
+
+		rv = OF_getencprop(node, "#size-cells", &size_cells,
+		    sizeof(size_cells));
+		if (rv <= 0)
+			size_cells = 1; /* Default size */
+
+		nbase_ranges = OF_getproplen(node, "ranges");
+		if (nbase_ranges < 0)
+			return (-1);
+
+		if (nbase_ranges == 0) {
+			/* Empty ranges; property means 1:1 mapping */
+			continue;
+		}
+
+		nranges = nbase_ranges / sizeof(cell_t) /
+		    (addr_cells + host_address_cells + size_cells);
+
+		if (nranges == 0 || (nranges > MAX_RANGES))
+			return (-1);
+
+		/* Copy ranges data into local buffer */
+		OF_getencprop(node, "ranges", base_ranges, nbase_ranges);
+
+		/* Parse bus and host addresses along with sizes */
+		for (i = 0, j = 0; i < nranges; i++) {
+			ranges[i].bus = 0;
+			for (k = 0; k < addr_cells; k++) {
+				ranges[i].bus <<= 32;
+				ranges[i].bus |= base_ranges[j++];
+			}
+			ranges[i].host = 0;
+			for (k = 0; k < host_address_cells; k++) {
+				ranges[i].host <<= 32;
+				ranges[i].host |= base_ranges[j++];
+			}
+			ranges[i].size = 0;
+			for (k = 0; k < size_cells; k++) {
+				ranges[i].size <<= 32;
+				ranges[i].size |= base_ranges[j++];
+			}
+		}
+
+		/* Remap through ranges property */
+		for (i = 0; i < nranges; i++) {
+			if (start >= ranges[i].bus && end <
+			    (ranges[i].bus + ranges[i].size)) {
+				/* Found matching range entry */
+				start -= ranges[i].bus;
+				start += ranges[i].host;
+				end -= ranges[i].bus;
+				end += ranges[i].host;
+				break;
+			}
+		}
+
+		if (i == nranges) {
+			/* Could not find corresponding range entry */
+			printf("%s: address space translation error\n",
+			    __func__);
+			return (-1);
+		}
+	}
+
+	*phys_addr = start;
+	return (0);
+}
Index: sys/dev/uart/uart_cpu_fdt.c
===================================================================
--- sys/dev/uart/uart_cpu_fdt.c
+++ sys/dev/uart/uart_cpu_fdt.c
@@ -47,6 +47,7 @@
 #endif
 
 #include <dev/fdt/fdt_common.h>
+#include <dev/fdt/simplebus.h>
 #include <dev/ofw/ofw_bus.h>
 #include <dev/ofw/ofw_bus_subr.h>
 #include <dev/uart/uart.h>
@@ -215,13 +216,20 @@
 	di->bas.bst = uart_bus_space_mem;
 
 	err = fdt_regsize(node, &start, &size);
-	if (err)
+	if (err != 0)
 		return (ENXIO);
-	err = fdt_get_range(OF_parent(node), 0, &pbase, &psize);
-	if (err)
-		pbase = 0;
 
-	start += pbase;
+	if (fdt_is_compatible(OF_parent(node), "simple-bus")) {
+		/* Get the physical base address of UART registers */
+		if (simplebus_get_base_addr(node, start, size, &start))
+			return (ENXIO);
+	} else {
+		err = fdt_get_range(OF_parent(node), 0, &pbase, &psize);
+		if (err != 0)
+			pbase = 0;
+
+		start += pbase;
+	}
 
 	return (bus_space_map(di->bas.bst, start, size, 0, &di->bas.bsh));
 }